This classic cheese sauce gets its distinctive flavor from mustard, Worcestershire and beer (we preferred a mild brown ale). Shred the cheese by hand on the large holes of a box grater. For more bite, use extra-sharp cheddar. Tossing the cheese with 1 teaspoon of flour ensured a smooth sauce. While we preferred thick, rustic slices of toast, a high­-quality supermarket sandwich bread worked, too. For a simple supper, spoon the rarebit on toast topped with sauteed mushrooms, sliced tomatoes and turkey or ham. The cooled sauce can be refrigerated for up to four days. To reheat, allow the rarebit to come to room temperature, then spread on toast and broil until browned and bubbling.