This is my recipe for cheese sauce. It makes enough for a single portion of macaroni or cauliflower cheese. It's not the cheapest thing in the world but it is tasty and gives me a great cheesy hit. It's also filling.
The cheese is the most expensive ingredient. I keep an eye open for special offers on really strong cheese because you get more flavour for your pennies, get a fair amount and grate and freeze it, writing the price per 10g on the container. I use Morrison's Savers Italian hard cheese which is OK for cooking - not great, but OK. Sainsbury's also does a value Italian hard cheese. I get the 'not- Parmesan' anyway, from choice, because the genuine stuff is not vegetarian friendly and I often cook for a vegetarian.
15g plain flour
10g Italian hard cheese, grated
40g strong cheddar, grated
pinch English mustard powder
(I don't add more salt as the butter and the cheese are salty)
In a non stick pan, melt the butter. Add the flour and stir it into a paste. Cook it out, stirring, for a short time.
Take the pan off the heat. Add a little of the milk and whisk it in, getting rid of the lumps.
Place back on the heat, add the rest of the milk, whisking all the time.
Bring it up to just under a boil, where the mixture will thicken.
Add the mustard, pepper, Italian cheese and 20g of the grated cheddar and mix well while the cheese melts.
Use the rest of the cheese to sprinkle over the top of whatever you are making with the cheese sauce.
(or - if one is both lucky and lazy, one bungs it all in one's Thermomix, sets it to 8 mins; 98 degrees; speed 4 and comes back 8 minutes later to a perfectly made sauce!)