Honestly, I practiced many mac & cheese recipes out on my dear husband before I stopped at this combination. It is sooo fabulous and creamy. Served at Thanksgiving and it was a HUGE success.
Cook the macaroni according to the directions on the package, but take them out a minute or so early as they will fully cook in the oven. Drain well.
Heat the milk in a small saucepan, but don't boil it. Melt 6 tablespoons of butter in a large pot and add the flour. Cook over low heat for 2 minutes, stirring with a whisk. While whisking, add the hot milk and cook for a few minutes until thickened and smooth. Off the heat, add the gruyere, cheddar, Fontina, ham, 1 tablespoon salt, 1/2 tsp each cayenne, pepper, and nutmeg. Add the cooked macaroni and stir well. Pour into a 13 x 9 pan.
Sprinkle panko and Parmesan on top and cut up the remaining butter and put on top. Bake for 30 to 35 minutes, or until the sauce is bubbly and the macaroni is browned on the top.