Makes ten to twelve portions.
1 teaspoon butter
8 slices white bread, crusts removed
1/4 cup mascarpone cheese
1 tablespoon chopped chives
4 ounces Fontina cheese, grated
4 ounces (6 or more slices) thinly sliced smoked Black Forest ham
1 cup cream or milk
Salt and freshly ground black pepper
1 tablespoon olive oil
Butter an 8-by-4-inch loaf pan and line with oiled parchment paper. Begin layering the croque monsieur by lining the bottom of the loaf pan with bread (use 2 slices for each layer). Dot the first layer with 1 generous tablespoon mascarpone cheese and spread as evenly as possible. Sprinkle 1 teaspoon of the chives over the cheese. Cover with 1/4 cup Fontina cheese and layer the ham over cheese. This is one complete layer. Build two more layers, ending with a row of bread.
Whisk together the cream or milk and eggs in a bowl to make a custard. Strain the custard through a sieve and season to taste with salt and pepper. Pour the custard over the croque monsieur, cover with parchment paper, and allow to rest in the refrigerator for at least 2 hours before baking. The croque can be placed overnight in the refrigerator at this point if desired.
Preheat the oven to 325 degrees. Place the loaf pan in a deep casserole and add enough hot water to come halfway up the sides of the loaf pan to create a bain-marie. Cover with a piece of buttered parchment paper. Bake for about 45 minutes to 1 hour or until the custard has set. Test with a toothpick -- if it comes out clean, remove from the oven and the bain-marie and allow the croque monsieur to cool in the loaf pan. When cool, place in the refrigerator to chill. Turn the croque out of the pan and cut into generous 1/2-inch-thick slices. Cut each slice in half across the layers and skewer the two halves together. (The slices can be left whole for a sturdier presentation.)
To serve: Heat an 8-inch sauté pan with 1 tablespoon olive oil and gently place the croque monsieur skewers into the pan; sauté until golden brown on both sides. Serve with a green salad.