Ingredients

• 6 tbsp unsalted butter, room temperature, plus more for dish
• 5 lb Yukon Gold potatoes, scrubbed
• ⅓ cup sour cream
• 4 oz cream cheese, room temperature
• 6 oz raclette or fontina, grated (2 ½ cups)
• ½ cup whole milk, room temperature
• Kosher salt and freshly ground pepper
• ⅓ cup extra-virgin olive oil
• 2 tsp minced garlic (from 2 cloves)
• 16 small whole fresh sage leaves, or 8 large leaves, coarsely chopped
• 2 tbsp finely chopped fresh chives, for serving

Directions

1. Preheat oven to 375°F Bake or 350°F Convection. Butter a 2-2 1/2-quart baking dish. Bake potatoes directly on rack until tender, 1 hour to 1 hour, 15 minutes. Remove and let cool slightly; when cool enough to handle, cut in half and scoop out flesh, reserving skins.
2. Rice or mash potato flesh in a large bowl; add butter, sour cream, cream cheese, half of raclette or fontina, milk, 2 tsp salt, and ¼ tsp pepper and mix until smooth and creamy. Transfer to prepared dish; top with remaining raclette/fontina.
3. Slice potato skins into 1 1/2-inch-wide strips. Transfer to a rimmed baking sheet; toss with oil, garlic, sage, and ½ tsp salt. Spread in a single layer. Place casserole and sheet pan of skins in oven and bake until cheese melts and skins become crisp and golden brown, 25 to 30 minutes. Sprinkle roasted skins over casserole; top with chives and serve.
4. Do Ahead: The potatoes can be made through step 1, covered, and refrigerated for up to three days; store the skins and flesh separately. Bring to room temperature an hour before baking, and increase the time by 10 minutes.