A white sauce is a sauce made using milk. It has a mild, creamy flavour that complements a range of ingredients, including mushrooms, chicken and fish.
The first thing to decide when making a white sauce is what kind of milk you want to use. If you’re using dairy, using skimmed milk will give you a very thin sauce, so I would recommend at least semi-skimmed. If you’re using a non-dairy milk, you need one with more fat and protein than sugar. This means that soy and nut milks will work, but things like coconut milk won’t. And, if possible, use an unsweetened milk.
The next thing to decide is how to flavour your sauce. I like to start a white sauce by gently frying some diced onion (cutting tutorial here) or crushed garlic in a little oil before I add the milk. You can also add a stock cube directly to the milk as you heat it – try and match the flavour of the stock to the ingredients you plan to put in the sauce. You could also add a little grated or cream cheese for richness, nutmeg for a little spice, or some dried parsley.
Finally, you’ll need to thicken your sauce. There are two main techniques you can use here.
The classic technique to thicken a sauce is called a roux. A roux starts by frying a spoonful of wheat flour in a little butter or oil. You have to be careful at this stage that the flour is cooked, or the resulting sauce will taste floury. You also have to be careful to avoid lumps – one way to do this is to add the flour to onions, rather than directly into the pan. After a few minutes of frying, you can add your milk. To avoid lumps (again), you need to add it very slowly at first, and keep stirring!
It can be quite easy to get a roux wrong, so the thickening method I prefer is cornflour. Simply mix together one spoonful of cornflour with one spoonful of cold water or milk. Then, add the cornflour mix to your sauce. The great thing about this method is that it can be done last-minute, there’s no floury aftertaste, it’s a lot easier to avoid lumps, and it’s even gluten-free!
Whichever method you use, a white sauce is really versatile. You can use it with all kinds of fish, in pasta dishes like lasagna, or in a chicken and mushroom pie…
One final thing though – if you have leftover white sauce you may find that it sets when chilled, especially if you used cornflour as a thickening agent. This is perfectly normal and doesn’t mean the sauce has gone off; it will go right back to liquid when you heat it up again.