Before you go and get intimidated, croque monsieur is just a fancy French name for a hot ham and cheese sandwich. Now, I don't tend to cook a lot of French cuisine in my house, except for the recipes from Mastering the Art of French Cooking by the one and only Julia Child. This sandwich is typically made with Gruyere cheese. However, it is one of those dishes that is open for interpretation and can be made to the cook's liking.
French bread (or whatever bread you have available)
Ham (thinly sliced)
Heat your oven to 375 degrees (F). Slice your bread (not too thick, but not too thin). Place your bread onto a baking sheet and toast for 3 minutes. Slice your onion and tomato. Saute your onion in butter. Remove your bread from the oven and spread about 1/2 tbsp of cream cheese on each slice of toasted bread. Top your bread with your onions, tomato, ham, and then cheese. Place back into the oven until your cheese is melted (I like mine to get all bubbly...this works best in the broiler for about 30 seconds). You can eat this as an open face sandwich, or use two pieces to make one sandwich. Try making this with provolone or mozzarella cheese, or even use salami, chicken, or roast beef. As Julia Child would say, "bon appétit!"