1 1/2 cups heavy cream
3 cloves garlic, minced
1/2 teaspoon dried thyme
Pinch of nutmeg
2 pounds russet potatoes, peeled and cut into 1/8-inch thick slices
Kosher salt and freshly ground black pepper, to taste
1 cup shredded Gruyere cheese
1/4 cup freshly grated Parmesan
1/2 teaspoon fresh thyme leaves
In a medium saucepan, whisk together heavy cream, garlic, thyme and nutmeg over medium heat until heated through, about 1-2 minutes.
Add a layer of potatoes to a 4-qt slow cooker in an overlapping pattern; season with salt and pepper, to taste. Pour 1/3 cup cream mixture over potatoes; sprinkle with Gruyere. Repeat with remaining potato slices, cream mixture and Gruyere to create 2 more layers.
Cover and cook on high heat for 4-5 hours, or until potatoes are tender. Sprinkle with Parmesan. Cover and cook until melted, about 5 minutes.
Remove lid and let potatoes rest for 15 minutes, allowing the sauce to thicken as it sits.
Serve, garnished with thyme, if desired.