4 chicken cutlets (1 pound total; about 1/4 inch thick)
1/2 teaspoon salt
1/2 teaspoon pepper
2 tablespoons unsalted butter
8 spinach leaves, trimmed
4 thin slices boiled ham (2 ounces)
3 ounces Gruyère, coarsely grated (1 cup)
Preheat broiler. Pat chicken dry and sprinkle with salt and pepper. Heat butter in a flameproof 12-inch heavy skillet over moderately high heat until foam subsides.
Sauté chicken in butter, without turning, until cooked through and undersides are golden, about 2 minutes. Remove from heat and turn chicken over, then top each cutlet with 2 spinach leaves, 1 slice ham (folding it to fit), and 1/4 cup cheese.
Broil 3 inches from heat until cheese is melted, 1 to 2 minutes.