Gruyere Rarebit with Ham

1 pound thinly sliced veggie ham, or wham slices
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 veggie 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.