THICKENING SAUCE: Don’t Roux the Day You Ruin Your Sauce

Red wine gravy in a gravy boat made from a roux

The roux is the best method of getting a thickener into your sauce without lumps and the raw taste of starch. Despite what you may have heard it is actually a very simple technique/recipe and can be used in a great many dishes from around the world…

The cooking world makes much of French cooking techniques. Not least of which include their sauces. Of course it would be almost as easy to say that such techniques are over-hyped ‘cheffy’ techniques, as much as it is par for the course to mention the importance of such techniques and how they are to the foundations of cooking.

To be honest both assertions would hold some truth. On one hand it must be said that all too much fuss is made about many cooking techniques, especially French ones, as we shall soon see it is quite easy to master much feared techniques with very little effort and huge pay-offs. On the other hand it cannot be denied, given the aforementioned pay-offs, that French cooking techniques have been a huge influence on cooking the world round, which are in fact used in many cuisines to make many dishes. No technique has such profound pay-offs as learning how to make and use a roux.

The fear of making gravy

Now I am sure you may have seen all the cheat gravy powders on supermarket shelves, you may have heard about the many pitfalls of making a gravy or béchamel, or even tried and failed miserably at this technique? Maybe you have heard a French cook tell you about the intricacies of the roux? You may be thinking that it is all too much hassle?

Well you would be wrong. The secret to making a good sauce thickener every single time, with added flavour, no clumping or luminess and extra rich creaminess, is a roux. A roux, despite what you may think, is actually very easy to master and will never fail you. It can be used in a great many dishes and is a fantastic thing to add to your cooking technique repertoire. There is a sound logic behind a good roux and why it is vitaly important to use this technique for thickening a great many sauces.

Why use any thickener is your sauce?

One of the key elements of a good sauce – apart from flavour of course – is consistency. Most sauces need to be a particular fluidity so that it can moisten your food at the same time as sticking/adhering to it. Which is why the structure of a good sauce is of uppermost importance.

There really are only a few ways to build structure in your sauce. You can reduce it to the point that it reaches the consistency that you require. But this involves having sufficient time to wait while this happens, and that you are after the intensity of flavour that is present upon the point of reduction at which your sauce reaches the right consistency.

Chances are that your sauce will be way over-reduced and too strong in flavour. Which is why so many good sauces rely upon the use of some sort of thickener. And there is one ingredient that thickens better than almost anything else – starch.

Starch the king of thickeners

Starch is the reason why you add a little of the cooking water from your pasta into your pasta sauce. It is used to thicken ketchup, gravies and white sauces. In fact starch is used in a great many sauces. Cornstarch, arrowroot, tapioca, potato starch, kudzu root and flour.

Unfortunately, starch can be a cruel mistress when you cook with her. The very nature that makes it such a good thickener – its ability to swell, suck up water and crystallise into a stable structure that holds onto water – is also what makes it so finicky.

Starch becomes water soluble at around 60°C  and in the case of starch thickeners will turn gloopy (potato starch can be used as wall paper paste for example). So when you throw some starch into your hot sauce to thicken, it will immediately turn gloopy forming a seal around a clump of starch that won’t even touch the sauce. This is what causes lumpiness. The first most common thing that can go wrong when you try and thicken a sauce.

The second thing that can go wrong is the floury taste of starch thickeners. The worst of this can happen when you get little lumps of uncooked starch (see previous problem), but can also happen because the raw taste of flour and other starches can take up to 40 minutes to cook in liquid.

Flour as a thickener

Now consider flour. Flour is used in a great many classic  sauces (particularly non-Asian ones). Flour out of all of the starch thickeners does not turn clear when cooked. So if you want an opaque sauce as opposed to a translucent one, then flour is the right starch to reach for.

Enter perhaps the most feared, most used – and to be frank – quite simple French cooking technique that is used the world round in many cuisines and many important and delicious recipes – the roux. Which is basically a mixture of 50% butter (or fat) and 50% flour that is fried off before adding it to a sauce.

A good roux will ensure that the flour wont clump as it is added to your sauce by coating all of the flour grains in fat, which will keep the grains separate and stop them clumping as you add them to your sauce. It will cook off the ‘bready’ flavour of the flour by gently frying the flour, which can turn your sauce doughy. It can even develop caramelised and nutty flavour characteristics depending on the type of roux you are making.

The secret to a good roux

There are many kinds of roux that differ in colour and flavour from a white roux right through to a brick roux – which is a dark brown colour. The darker the roux the longer it will have cooked for – a brick roux, for example, will have to be cooked for over an hour. The darker roux will also have a lot stronger caramelised and nutty flavours which will enhance the flavour of your dish. But it will also have far less thickening power, with a white roux having about 4 times the amount of thickening power as a brick roux.

Wow, so there are many different kinds of roux that can be used in a seemingly endless amount of dishes from a multitude of gravies, béchamel, mornay sauce, cheddar sauce and soubise to mention a few; which are all used in a great many dishes including roasts, pies, lasagne, cannelloni, moussaka, mac ‘n’ cheese and cauliflower cheese again to mention but a few.

But in reality all of these sauces are slight variations on two things. You either add your roux to cooking juices in a pan with a little stock and maybe some wine to make a gravy – which will generally be brown in colour. Or you add milk to the roux to make a white sauce (aka béchamel) to which you can then add onions (soubise), cayenne, gruyere and parmesan (mornay) or cheddar cheese (cheddar sauce).

Personally, I can’t really be bothered with the rigmarole of cooking a roux long enough to develop it past a white roux (which takes about 5 minutes all up to make). My best tip for you if you feel the same, but want the extra nutty flavour in your sauce but with the maximum thickening power is to cook your butter into a buerre noisette (i.e. until it is brown and smells like roasted hazelnuts) before adding your flour. This will only take a few minutes and will be well worth the extra hint of flavour that gets added to your dish.

 How to make a roux

So here is the simple technique for making the perfect roux every time: 50% butter (You can use any type of oil or fat if you wish) and 50% flour.

Heat the butter in a pan – I like to do this for about 5 minutes until the butter is golden brown and nutty in flavour. But you can skip this step if you wish.

Add the flour and stir briskly with a whisk. Make sure all of the flour is coated in butter. You will need to continue to stir constantly for about 2 minutes until you notice the roux suddenly become looser and more moist. This will be the point at which each flour grain is coated in fat. And the flour will start cooking at this point.

Keep cooking for another 2-3 minutes minimum to cook out the raw taste of the flour – at which point you will have a white roux. Depending on how dark you want a roux you can keep cooking it for over an hour (I would suggest moving it to an oven at 180°C.

If you want to make a béchamel (or white sauce) which can in turn be made into a variety of other sauces just add milk. The ratio of milk to flour is about 8:1.

So, for example, if you had 4 tbsp flour and butter in your roux (about 1/4 cup) you would add approximately 2 cups of milk. But of course your roux will take less milk depending on how long you have cooked your roux for. Even things like humidity can effect the thickening power of flour. So always only add a little bit of liquid (including milk) at a time to your roux. So that you don’t over thin your sauce. It is easier to thin a sauce than thicken it. You don’t wast to have to make more roux now do you? Adding a little liquid at a time will also further decrease your chances of getting lumps.

Red wine gravy in a gravy boat made from a roux

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11 thoughts on “THICKENING SAUCE: Don’t Roux the Day You Ruin Your Sauce

  1. My roux separated (butter & flour) and then turned Rock-hard. What caused this? Was my old flour the cause? I used 1-1/4 sticks of butter, heated to bubbling, then slowly whisked in 8 ounces of flour. Then continuously stirred. I’ve made roux many times before with no problem (using 3 Tbsp. butter with about the same amount of flour, but adjusting if the result didn’t look right). But the amount needed for a Thanksgiving turkey gravy came from an article I read. Could the small stainless steel sauté pan be a factor (for this large amount)?

    • Hello Patricia,

      Thanks for your question : )

      I have never had roux split on me. But it usually happens when you add the milk or stock. Is this what happened to you? It is important to ensure the temperature of the milk/stock is cold or only slightly warm otherwise it may cause splitting.

      But it sounds like the splitting hapoened before you added any liquid from your description? And then it went rock hard?! Another possibility is that there was too much liquid in your butter. Some low quality butters have a lot of liquid (ie less fat content hence making them cheap) and I am thinking maybe this could have cause your problems. Much like adding water to flour makes a glue ie causes it to go rock hard. A way to stop this is to either use better quality butter or to evaporate the liquid from the butter by hearing it for about 10-15 min at a low temp (to stop it burning).

      I hope that helps?


      • Would using clarified butter eliminate the too much water problem?
        Note: I didn’t add any liquid (didn’t want to wreck the homemade turkey stock–so I used cornstarch to thicken it instead). My research found one comment about old flour, as well as the following:

        “When you gelatinize the starch you actually bust the starch granule. When you further cook it you break it down further into its sugar components like dextrose and such. If roux separates, you have too much fat (butter)—The extra fat didn’t have the opportunity to bind with flour.”

        So from this it looks like my roux could have broke down into dextrose, which is sugar, which could harden. And I think I had too much butter for the amount of flour–resulting in the roux “breaking.”
        Does this make sense?

  2. hey i made white roux sauce. when cooking the sauce, i kept on stiring but the it never became a smooth texture. My end texture was like a dough. there was a lump of the sauce on my table and i could even pick it up while it stays in shape. is it because i added too much milk? i don’t know what happen please help me understand the process

    • Hello Assya – it sounds like you did not add enough butter. Did you do 50% butter 50% flour? You then need to cook this for at least 5 minutes or until the mixture starts to “loosen” and then you can slowly add the milk a little bit at a time. Without enough butter the gluten in the flour is formed as you mix in the milk making it into a dough.

  3. You used the word ‘rouse’ in the ‘making a roux’ article. Is that a typo or an actual word? i.e. Roux is plural, rouse is singular, LOL?

    • Any high starch flour will work eg wheat, rice, corn starch, potato starch etc. But there are slight differences so you may have to vary the technique of making it slightly and I don’t know hat the flavour will be like for non-wheat recipes.

  4. I tried an apple pie filling recipe that had, what I believe, was a roux. It was butter, flour, brown sugar, white sugar, and water. The roux clumped up and never caramelized into the liquid I was supposed to be able to pour over the lattice pie crust. I was very frustrated. I’ve made roux’s before with no issues. The frustrating part was this recipe had over 16k likes on a popular cooking site and no one else seemed to have my problem.

    • Hello Kelly, the secret is to properly cook the flour in the butter until the oil starts separating out before adding anything else. Whether you add the sugar before adding the water or after would depend on the type of caramelisation you are after I guess. When you add the water you have to do it a small amount at a time making sure all lumps were gone before adding more.

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