How to make a roux sauce

It is worthwhile learning how to make a home-made white sauce based on a roux.  Roux is simply the French derived word for a mixture of melted butter and white flour. It is the roux that thickens the milk. What happens is amazing and very useful.

Start with accurately weighed ingredients. 30g white plain flour with 30g butter (do not use low fat spread) Have ready 300ml milk.

  • Use a small pan and melt the butter gently to prevent it burning
  • As the melted butter takes up the dry flour the mixture becomes like a paste, that is the roux
  • It seems unlikely that you will ever get a smooth sauce at this stage but persevere. Gradually add the milk about 2 tablespoons at a time and stir to absorb it into the roux.
  • 300ml (half a pint) can be thickened with this roux to make a sauce that will coat vegetables or fish.
  • As you add the milk maintain the heat, putting the pan over the heat and taking it off to beat the sauce in order to prevent lumps. Keep adding the milk and look at the sauce to see how it is becoming thicker and smoother.
  • Finally all the milk will have been added and you can bring the sauce to the boil. This is important to ensure that all the starch grains in the flour have burst. Stir well. Remove from the heat and add seasoning such as white pepper (unless you want black speckles in the sauce) some salt and maybe other flavours such as chopped parsley, or grated cheese.

Cooks know how:

Scientifically the starch grains are responsible for the thickening of a sauce. The starch absorbs and swells due to the liquid. As the heat is increased the starch grains burst and thicken the mixture. Uncooked starch grains taste raw and therefore it is important to boil the sauce to ensure all starch grains are cooked. White flour gelatinises around boiling point. A thickened sauce sets on cooling and returns to fluid on heating

Making a flavoured roux:

You can cook something such as finely chopped onions or mushrooms in the butter and then add the flour and create the roux sauce. Follow the same method as with a plain white sauce but allow the vegetable to cook (use about 15g more butter with mushrooms as they absorb the fat quickly)

  • Remember to re-boil and to stir well.
  • Seasoning your sauce is important

Uses for a white sauce:

Cauliflower cheese, Lasagne, Fish and parsley sauce, Vol au vent, Pasta bake, Onions in cheese sauce.

Using a basic roux with different amounts of milk can give you a pouring sauce (400ml milk), a coating sauce (300ml as recipe) or a very thick sauce, binding sauce (200ml milk) to combine other ingredients for pastry fillings.

See recipe for Bechamel sauce.