This is the basic sauce for a number of other recipes and it's fairly easy to make. For a vegan option, you can use soya milk or any other vegetable milk (how about home made walnut and oat milk?). I've tried it and it's not bad at all. The basic sauce is quite plain so it's best to add some flavouring. Cheese is probably the most popular for dairy sauces and there are a few recipes here for things with cheese sauce. Don't be put off, however, if you don't eat cheese - you can still try all the recipes using, for example a half teaspoon of mustard powder and some fried onions in place of the cheese (this is nice with cauliflower). Finely chopped celery or mushrooms are also good and nuts are great, especially with some fresh green herbs. Have a look at my recipe for cabbage and pine nut bake for an example of a vegan white sauce recipe.
In the list of ingredients below, you'll notice I say 'liquid' rather than milk. This isn't just to suit the vegans - even if you are using milk, you can dilute it with water or, better, vegetable stock. This is a particularly good idea with cauliflower, which produces delicious stock. It also contains a lot of vitamins and minerals from the vegetable even if you have just steamed it gently for a few minutes, so it's better to use it than pour it away.
The quantities given will produce about a litre of thick sauce. If you don't use it all at once it will keep in the fridge for a few days or you can freeze it.
3 tablespoons of vegetable oil, butter or margarine
3 heaped tablespoons of flour
3 large mugs of liquid
Use a heavy sauce pan if you've got one - I've got a cracking heavy duty, enameled iron thing left over from the cold war. Sveta brought it with her when we moved in to our new flat. Melt the butter or margarine first if you're using it, then add the flour and mix it together. You should have a blobby thing with a pasty consistency which holds together well but doesn't stick to the pan - this is called a roux and the thing to bear in mind when dealing with such a beast, is to keep stirring it around so it doesn't burn - keep your pan on a medium heat and after 5 minutes or so, your roux will start to break up. This stage is important, as it means the flour is cooked and if you try to make a sauce without cooking the flour properly, your final result will almost certainly be lumpy. It might turn out lumpy anyway but you want to be in with at least a fighting chance.
Once the roux has started to break up, swirl it around for another minute just for luck, then pour in all the liquid. You can turn the heat up now to bring it to the boil faster, but it's really important to keep stirring the mixture. I find a wooden spatula is perfect for this as it stops the stuff from sticking to the bottom of the pan, which can be fatal. When the sauce boils it's just about ready. Turn the heat down and stir for a couple of minutes to beat out any lumps (ha, ha - they always say that in cookery books. If you've still got lumps in your sauce at this stage, just ignore them, they won't go away).