What is in the recipe known as Welsh Rarebit?

Ingredients:

* 1 tablespoon unsalted butter

* 1 tablespoon all-purpose flour

* 1 cup milk

* 1/2 teaspoon salt

* 1/4 teaspoon black pepper

* 1/2 teaspoon Worcestershire sauce

* 1/2 teaspoon dry mustard

* 1 cup shredded sharp cheddar cheese

* 1/4 cup grated Parmesan cheese

* 2 slices whole-wheat bread

* 1 tablespoon chopped fresh chives, for garnish

Instructions:

1. In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1 minute, or until the mixture is thickened and bubbly.

2. Slowly whisk in the milk and bring to a simmer. Cook, stirring constantly, until the sauce has thickened, about 5 minutes.

3. Season the sauce with salt, pepper, Worcestershire sauce, and dry mustard. Stir in the cheddar and Parmesan cheeses until melted and smooth.

4. Toast the bread slices and place them on two plates.

5. Pour the cheese sauce over the toast and garnish with chives. Serve immediately.