Cheese Lover's Fontina and Mozzarella Grilled Cheese Sandwich

slices bread (I used a soft, small French baguette; use your favorite)

to 2 tablespoons butter, softened for generous spreading (I use unsalted butter)

about 1 to 2 ounces sliced fontina cheese, or enough to cover every inch of bread

about 1 to 2 ounces grated mozzarella cheese, enough to loosely pile 1 to 2 inches high