8 slices good quality white loaf bread
1 small red onion, minced
1/2 cup mayonnaise
2 teaspoons whole-grain mustard
1/2 cup grated Parmesan cheese
Ground black pepper
Adjust oven rack to middle position and heat oven to 425 degrees. Use a 2-inch biscuit or cookie cutter to cut 24 bread rounds; place on a cookie sheet and bake until golden brown. Remove toasts from oven and turn oven to broil.
Meanwhile, mix onion, mayonnaise, mustard, 1/4 cup of the Parmesan cheese and a few grinds of pepper. Spread a portion on each toast round and sprinkle with remaining cheeses. Broil until bubbly and lightly spotty brown, 2 to 3 minutes. Serve.