Sautée the potatoes in butter, with the onions and the pancetta, and once they are nicely cooked and browned, put them in an oven-safe dish.
Add slices of Taleggio on top of the potato mixture; you need to be generous!
Keep adding layers until you reach the top of the pan and finish with cheese.
Bake at 375℉ for 40 minutes or until the cheese is melting and begins to crisp a little. Enjoy warm with a green salad on the side!