Potatoes Au Gratin Recipe

Ingredients

• Butter for the baking dish
• 2 tablespoons unsalted butter, melted
• 1 cup panko breadcrumbs
• 1 1/2 cups (6 ounces) grated Gruyere cheese, divided
• 2 1/2 cups heavy cream
• 1/2 cup milk
• 3 sprigs thyme
• 3 pounds Yukon gold potatoes, peeled and cut into 1/8-inch-thick slices
• 1 medium yellow onion, cut into 1/8-inch-thick slices
• 1 teaspoon salt
• 1/8 teaspoon ground black pepper