Carole's Famous Updated Cheese Potatoes

1. Heat oven to 350 degrees. 2. Meanwhile, melt butter in large Dutch oven over medium-high heat until foaming subsides, about 1 minute. Add onion and saute until it turns soft and begins to brown, about 4 minutes. Add garlic and saute until fragrant, about 30 seconds. Add cream, milk, nutmeg, salt, pepper, and potatoes and bring to simmer. Cover, adjusting heat as necessary to maintain light simmer, and cook until potatoes are almost tender (paring knife can be slipped into and out of center of potato slice with some resistance), about 15 minutes. 3. Transfer potato mixture to 3-quart gratin dish and layer with Swiss and Mozzarella cheese. Top with Parmesan. Bake until cream has thickened and is bubbling around sides and top is golden brown, about 20 minutes (OR MORE with our oven). Cool for 5 minutes before serving. Also, consider adding a bit of spiciness - add some diced jalapenos to them (without the seeds).