Welsh rarebit is a dish that is typically made with toasted bread and a cheese sauce that may include mustard and/or beer. Some recipes call for a thinner sauce that is poured over the bread. Other recipes call for a thicker cheese sauce and for the dish to be broiled until the cheese bubbles and turns crispy.
To make a basic Welsh rarebit recipe, brush slices of crusty white bread with butter, and bake them until they're brown. Melt 1 tablespoon of butter in a small saucepan, add 1 tablespoon of flour and whisk until the mixture is light brown. Whisk in 1 teaspoon of dry mustard and 1/2 cup of dark stout beer, or substitute 1/2 cup of milk for the beer. When the mixture is bubbling and smooth, stir in 1 1/2 cups of shredded sharp cheddar cheese. Pour the sauce over the bread, and eat it as is, or broil it.
The cooked cheese sauce burns quickly under the broiler and should be watched closely. It should only take one to three minutes to be ready.
Plenty of Welsh rarebit variations exist. One early recipe called for the bread to be soaked in red wine. Some people layer tomato, turkey or bacon between the bread and cheese, and some top Welsh rarebit with fried egg.