INGREDIENTS
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1 teaspoon unsalted butter
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4 cups heavy cream, or more as needed
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2 teaspoons salt
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1 teaspoon freshly ground black pepper
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1 1/2 pounds Idaho potatoes, peeled and cut into 1/4-inch slices
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1 1/2 pounds sweet potatoes, peeled and cut into 1/4-inch slices
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8 ounces Swiss cheese, grated