Scalloped Potatoes with Gruyere Recipe

Ingredients

• 2 tablespoons extra virgin olive oil
• 4 cups thinly sliced onions (sliced crosswise, see how to slice onions)
• 6 medium-small Yukon gold potatoes (about 1 1/2 pounds), peeled, thinly sliced (1/8-inch thick, it helps to use a mandoline)
• 3/4 cup grated Gruyere cheese, divided 1/2 cup, 1/4 cup
• 1/2 cup grated Parmesan cheese
• 1 teaspoon salt
• 1/2 teaspoon white pepper (or black pepper if that is what you have)
• 1 teaspoon of butter to butter the gratin or casserole dish
• 1/3 cup stock (chicken, beef, or vegetable stock, use vegetable stock for vegetarian option)
• 1 teaspoon finely minced fresh rosemary