Preheat the oven to 350°F
Use a mandoline to slice 6-8 large russet potatoes thinly.
Put the sliced potatoes into a large bowl. Drizzle 2 tablespoons olive oil over them.
Toss in generous amounts of salt, pepper and 2 tablespoons chopped rosemary. Then move it around with your hands until all slices are coated.
Use the olive oil to add 1 tablespoon to a 12-inch cast iron skillet, or an ovenproof skillet.
Place the potatoes vertically in the skillet, starting at the outer edge and working your way to the center.
Mix 1/2 large sweet onion (thinly cut) with 6-8 large garlic cloves. Place the garlic slices and onions between the potatoes in the pan.
Combine 1 cup of lightly softened butter with 1 1/2 cups grated white cheese cheese and 1 1/2 cups grated Parmesan cheese in a medium-sized bowl.
Use a small amount of the cheese mixture to press between two slices of potato. Place the rest of the cheese mixture on top.
Bake for one hour and twenty minutes. For the final 20 minutes, foil the potatoes to stop them from browning. Cook the potatoes until they are tender and crispy on top.
Warm with sour cream, chives (optional).
Enjoy!
