Preheat oven to 425˚ F. Butter an 11x7-inch baking dish and set aside.
Combine sliced potatoes and onion in a large pot. Add enough water to cover. Bring water to
a boil. Add 1 tablespoon kosher salt, reduce heat and simmer until potatoes are almost tender,
about 5 minutes. Drain potato onion mixture well and discard water.
Arrange half of the potato onion mixture in the baking dish. Sprinkle with salt and pepper. Sprinkle
with ½ cup Gruyère cheese and 2 tablespoons Parmigiano-Reggiano cheese. Arrange remaining
potato-onion mixture on top. Pour cream over. Sprinkle with salt, pepper and nutmeg. Top with
remaining cheeses and panko. Bake gratin, uncovered, until cream thickens, the potatoes are
completely tender when tested with a knife, and the top is golden, about 25 minutes. If browning
too early, cover loosely with foil. Remove from oven and cool for 5 min before serving.
Recipe by Draeger’s Cooking School
