- 1 pound thinly sliced ham
- 2 tablespoons unsalted butter
- 2 tablespoons all-purpose flour
- 3/4 cup whole milk
- 2 teaspoons dry mustard
- 3/4 cup beer (not dark)
- 6 ounces coarsely grated Gruyère (2 cups)
- 4 oval slices pumpernickel or rye bread
- Garnish: cornichons or gherkins
- Preheat broiler. Wrap ham tightly in foil and put on rack of oven farthest from broiler to heat through, about 15 minutes.
- Meanwhile, melt butter in a heavy medium saucepan over medium-low heat until foam subsides, then whisk in flour and cook, whisking, 1 minute. Whisk in milk, mustard, and 1/4 teaspoon pepper and bring to a boil over medium heat, whisking. Simmer, whisking, 2 minutes, then add beer and simmer, whisking, 1 minute. Remove from heat and whisk in cheese until melted.
- Arrange bread in 1 layer on a baking sheet and broil 4 to 5 inches from heat, turning once, until lightly toasted, about 5 minutes total.
- Transfer bread to plates and spoon some of sauce over it, then top with ham and remaining sauce.