Cut the slices of ham in half so that they are the same size as the bread slices.
In a skillet, lightly fry the slices of bread in a little oil.
Making the béchamel sauce
Melt the butter in a saucepan over low heat. Add the flour and stir. Cook for 2 minutes without letting it brown.
Add the grated Gruyère cheese (see the amount listed for the béchamel sauce in the ingredients), and stir well to incorporate it into the béchamel sauce.
Assembly and baking
Preheat the oven to 180°C (convection) or 200°C (conventional).
Place half of the bread slices on a pizza pan or in a greased baking dish. Spread a thin layer of béchamel sauce on each slice, then add a slice of ham and a slice of Emmental cheese. Top with a second slice of bread, spread béchamel sauce over the top, and sprinkle with grated Gruyère cheese.
Place the dish in the preheated oven on the second rack from the bottom. Bake for 10 minutes.
Keep an eye on them while they bake so they don't burn!
Serve these croque-monsieurs piping hot, along with a seasonal salad.