Elise Bauer

INGREDIENTS

2 tbsp

olive oil

4 cups

thinly sliced onions (sliced crosswise, see how to slice onions)

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 tsp

salt

1/2 tsp

white pepper (or black pepper if that is what you have)

1 tsp

butter to butter the gratin or casserole dish

1/3 cup

stock (chicken, beef, or vegetable stock, use vegetable stock for vegetarian option)

1 tsp

finely minced fresh rosemary