Categories: Sides
Ingredients
- 5 tbsp. unsalted butter, softened and divided
- 1 1/2 lbs. medium Yukon gold potatoes, peeled
- 1 1/2 lbs. medium sweet potatoes, peeled and halved lengthwise
- 1 3/4 cups heavy whipping cream
- 1/3 cup minced garlic
- 1 tbsp. chopped fresh sage
- 2 tsp kosher salt
- 2 tsp chopped fresh thyme
- 1/2 tsp black pepper
- 1/4 tsp ground nutmeg
- 1 cup shredded Gruyere
- 1/2 cup shredded Parmesan
- Garnish: chopped fresh sage
Directions
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Preheat oven to 400. Spread 1 tbsp. butter in bottom and up sides of an 11×8-inch baking dish; place on a rimmed baking sheet. Fill a large bowl with cold water.
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Using a mandolin or very sharp knife, carefully cut potatoes crosswise into 1/8-inch thick slices. Add potatoes to bowl of cold water as you work.
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Drain potatoes well, and thoroughly pat dry. Layer half of potatoes in bottom of prepared pan as desired.
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In a medium saucepan, heat cream, garlic, sage, salt, thyme, pepper, nutmeg, and remaining 4 tbsp. butter over medium heat just until bubbles form around sides of pan. Gradually pour half of cream mixture all over potatoes in pan; sprinkle with half of Gruyere. Repeat layers with remaining potatoes, remaining cream mixture, and remaining Gruyere. Sprinkle with Parmesan.
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Spray a piece of foil with cooking spray; cover pan with foil, spray side down. Using a wooden pick, poke several holes in top of foil.
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Bake for 40 minutes. Uncover and bake until potatoes are tender and sauce is golden brown and bubbly, 25-30 minutes more, re-covering with foil to prevent excess browning, if necessary. Let stand for 30 minutes. Garnish with salt.