A roux (pronounced 'roo') is the name given to the cooked mixture of butter and plain flour that thickens and forms the base of various sauces, particularly the white sauce (béchamel). It's also an essential ingredient in classic recipes like a classic lasagne, fish pie, moussaka, macaroni cheese and cauliflower cheese.
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It consists of equal quantities of butter and plain flour. The fat is melted, the flour is mixed through over a gentle heat. Hot liquid is then gradually mixed into the paste to make a silky sauce which needs a few minutes more cooking before serving or using.
What are the right ratios for a roux?
Use an easy-to-remember equal quantity of flour to butter. This gives a good all-round thick, paste and makes it easier to incorporate the liquid. Your mixture will be less likely to go lumpy.
A good ratio for a basic sauce is:
- 50g butter
- 50g plain flour
- 500ml whole milk
Try our easy white sauce recipe for a step-by-step guide to velvety smooth sauce. Want an easy to follow video tutorial? Watch our video and learn how to make our easiest ever white sauce.
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How to get a lump-free sauce
Roux-based sauces have a reputation for going lumpy but there are a few things that help to stop lumps forming.
- Adding hot liquid to a hot roux stops the butter from clumping and causing lumps.
- Adding the liquid gradually to start and mixing well between each addition.
- Whisking rather than stirring the sauce it cooks helps to knock out any lumps.
If all this fails you and you are left with a few lumps, then you can always sieve the sauce into another pan to make it lump free.
How to cook a roux
Once you've combined the flour and melted butter, the roux needs to be cooked for at least 2 minutes to cook out the raw flour. You can then choose to add your liquids to create a sauce or even continue cooking the roux. Cooking it until it has a rich, caramel colour will give your sauce a slightly nuttier flavour.
Flour and fats
Butter: use an unsalted full-fat butter. You’re only making a base, and you can add seasoning later on in the method.
Dairy-free spread: if you're making a sauce that needs to be vegan or dairy free, you can easily make a roux with a dairy-free butter alternative. Try using the butter-flavoured ones rather than ones made with coconut oil.
Flour: always use plain white flour. Self-raising flour has raising agent in and will leave your finished sauce with a slight taste of bicarb.
Using stock in a roux
The white sauce and its derivatives are the most common ways of using a roux, but you can also use stock instead of milk for the base to a pie filling, or make a flavoured sauce called a velouté, which is normally enriched with cream.
Roux-based recipes to try
1. Cheese sauce
Make this basic cheese sauce with our easy recipe and add it to other dishes like cauliflower cheese and gratins. This is a great storecupboard recipe to have in your repertoire as it has so many uses. It's loaded with strong cheddar cheese and ready in just 15 minutes.
2. Lasagne
A classic, comforting lasagne is filled with a rich ragu and a smooth creamy sauce. It's a perfect warming dish for the whole family – just bake until golden and bubbling, then serve with pride.
3. Ultimate macaroni cheese
Who doesn’t love a cheesy baked pasta? This nostalgic macaroni cheese is topped with baked tomatoes and plenty of gruyère. The ultimate indulgence on a chilly evening. This foolproof recipe has three types of cheese for an extra flavour boost.
Mastered this technique? Try our other essential cooking tips...
How to make hummus
How to make caramelised onions
How to make mulled wine
How to make the ultimate gravy
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What's your favourite recipe using a roux? Leave a comment below...
