From 1922:
Melt 1 oz. of margerine in a pan, and stir in 1 oz. of flour and blend well; add about 1 gill of milk gradually (off the fire) ; stir until boiling, simmer for two or three minutes, then add 3 oz. of grated cheese, 1 teaspoonful of made mustard and a little pepper. Stir until the cheese melts. If too thick, add more milk. Spread on buttered toast, and lay the bacon (which should be rolled and fried or baked) on the top. Serve hot.