WELSH RABBIT aka Rarebit
by Nana Principe
1 Tablespoon butter
l Tablespoon flour
l Cup milk
l cup or more of cheese (cheddar is best) cut into small pieces
1/8 teaspoon salt (optional)
1/8 teaspoon dry mustard (optional) a bit of Grey Poupon can be used instead
¼ teaspoon Worcestershire Sauce (optional)
Pepper (to your taste) or omit
Return to my den
Melt butter over low heat, stir in flour to make a paste, add milk gradually, stirring all the time until thick;  then add cheese and seasonings. 
Pour over crackers or  toast for serving.  A slightly beaten egg may be added just before serving, cook well after adding.
This is the sauce I use over Asparagus for Asparagus on Toast. Also can be mixed with cooked elbow macaroni, topped with buttered crumbs and baked to make Macaroni and Cheese.