# Preheat a panini maker, double-sided electric grill, or a grill pan or heavy skillet.
# Meanwhile, brush both sides of each slice of bread with olive oil or butter. On one of the slices, evenly assemble the sandwich layers: smoked Gouda, prosciutto, onions, tomato, fontina, and the second bread slice.
# Place the sandwich in the panini maker, double-sided grill, or on the grill pan or skillet; close the machine or place another heavy pan on top of the sandwich in the pan or skillet. Cook until the sandwich is crisp and golden on both sides; if it is being cooked on the stovetop, carefully lift off the top pan and use a spatula to flip over the sandwich to crisp the other side. Serve immediately.
About This Recipe
A Panini Maker adds extra ease to the preparation of this simple, delicious sandwich, though you can also cook it in a skillet or grill pan weighted down with another heavy skillet or in a double-sided countertop electric grill. The pressure exerted on the sandwich helps it develop a very satisfying crustiness. If you like, you can serve panini such as this cut into squares as appetizers for an informal party.