Au Gratin Potato Stacks

Ingredients

• 1 tbsp salted butter, melted
• 2 tbsp salted butter
• 1 ½ cups heavy whipping cream
• 4 cloves garlic, finely sliced
• 4 sprigs fresh thyme, plus additional for garnish
• 2 sprigs fresh sage
• 1 tsp coarse kosher salt
• 1 tsp ground white pepper
• 4 to 5 medium red potatoes, cut into ¹⁄₈-inch-thick slices
• 2 cups shredded Gruyère cheese
• ¼ cup freshly grated Parmesan cheese
• Crème fraîche, for serving