The base of this sauce is a classic Bechamel, then simply adding processed cheese slices and seasonings. Seasonings is where the customisable part comes in; you can have it plain or experiment with different spice combinations or even herbs.
(Inspired by a recipe from a work friend, Rosemary Waight).
25g unsalted butter,
25g plain flour,
250g whole milk,
6 processed cheese slices (the type used on burgers),
1tsp smoked paprika,
1/2tsp cayenne pepper,
Salt and pepper, to taste
In a saucepan, melt the butter then stir in the flour and cook for a couple of minutes, creating a roux (this cooking stage will stop the final sauce having a floury texture).
Gradually add the milk a little at a time and use a whisk to combine with roux. Make sure the previous bit of milk has been incorporated before adding more, this will stop the sauce from going lumpy.
Once all the milk is in, throw in the cheese and spices and continue to whisk until the cheese has melted in. You should now have a smooth, gooey sauce.
Season with a little salt and pepper, and give it a taste. Then add more seasoning if needed.