- Preheat oven to 350°F. Grease a 3-quart baking dish or gratin dish. Layer half of the sliced potatoes, butternut squash, and leeks in the prepared dish. Sprinkle with half of the sage, garlic, salt, nutmeg, and pepper. Sprinkle with half of the cheese. Repeat layers. Pour whipping cream over top. Cover tightly with foil.
Preheat oven to 350°F. Grease a 3-quart baking dish or gratin dish. Layer half of the sliced potatoes, butternut squash, and leeks in the prepared dish. Sprinkle with half of the sage, garlic, salt, nutmeg, and pepper. Sprinkle with half of the cheese. Repeat layers. Pour whipping cream over top. Cover tightly with foil.
- Bake, covered, for 80 minutes. Uncover; bake about 30 minutes more or until potatoes are tender when pierced with a fork and top is golden brown. Let stand for 15 minutes before serving. If desired, top with additional sliced leek that has been sauteed in olive oil.
Bake, covered, for 80 minutes. Uncover; bake about 30 minutes more or until potatoes are tender when pierced with a fork and top is golden brown. Let stand for 15 minutes before serving. If desired, top with additional sliced leek that has been sauteed in olive oil.
To Make Ahead:
Slice potatoes, butternut squash, and leek. Place potatoes in a bowl of water to cover; cover bowl. Place squash and leek in separate airtight containers; cover. Store in the refrigerator for up to 24 hours. Drain potatoes well; pat dry with paper towels. Continue as directed.