Bacon and Mushroom Potato Gratin

INGREDIENTS

• 16 ounces thick-cut bacon, diced
• 1 medium onion, diced small (about 1 cup)
• 12 ounces cremini mushrooms, coarsely chopped
• 2 garlic cloves, minced
• 1 teaspoon chopped fresh thyme
• Salt and pepper, to taste
• 1 cup heavy cream
• ½ cup whole milk
• Pinch ground nutmeg
• 2 pounds Yukon gold potatoes (about 6 potatoes), sliced ⅛-inch thick
• 8 ounces Gruyère cheese, shredded (about 2 cups)