A very traditional, cheesy Welsh Rarebit, made with beer or milk.
Add the cheese, Worcestershire sauce, mustard, cayenne, and flour to a medium-sized saucepan. Mix well. Add 1/2 cup beer (or milk) and mix together.
Stir over a very low heat until just melted. Add more beer or milk if desired. Remove from heat and continue to stir for a minute. Let cool slightly (mixture will thicken) and pour over the toasted bread.
If desired, place the Rarebit covered toast under a broiler until bubbly and browned.
Don’t overthink or overheat the Welsh Cheese Rarebit. As soon as it’s melty take it off the heat. It will seize up and get grainy if overheated.
Welsh Rarebit is best used at once and is tricky to reheat. Reheat on the stove, very slowly, and as the mixture gets a little liquidy around the edges, remove the pan from the heat and whisk it. You might need more liquid.