Instructions

• Preheat oven to 400°F.
• Peel and thinly slice all four potatoes, keeping separated by color.
• In a 10-inch round (or similar-sized) deep casserole, place half the white potatoes on the bottom in a thin layer, overlapping slightly. Sprinkle with salt, pepper, 1 1/2 teaspoons chopped rosemary, and a grating of nutmeg.
• Next, cover with a layer of half the sweet potatoes; sprinkle with salt, pepper and 1 teaspoon chopped rosemary.
• Repeat layering using up all remaining potatoes, sprinkling each layer with salt, pepper and rosemary.
• Pour cream over potatoes and cover casserole with lid (or foil). Bake for 1 hour to 1 hour 15 minutes (see notes).
• Meanwhile, mix the grated cheeses. Remove the top and check the potatoes for doneness (if not tender, return to the oven for a bit). Sprinkle the cheese mixture evenly over the top, then return to the oven, uncovered, for 3 minutes, or until cheeses are nicely melted and bubbly.
• Serves 8.
• Notes:
• • Baking time will vary depending on your casserole and your oven. Test the potatoes with a fork or knife for doneness. A little overdone is better than a little underdone.
• • If making this in a smaller casserole (8-inch square, for example), reduce the cream and cheese proportionately. There will be leftover potato slices that you can use for another purpose.
• • This dish can be made in advance and reheated.