Cheesy Scalloped Potatoes with Caramelized Onions

Bahan-bahan (8 porsi)

• 3 tablespoons salted butter
• 1 yellow onion, thinly sliced
• kosher salt and black pepper
• 1/4 cup dry white wine, such as Pinot Grigio
• 1 clove garlic, chopped
• 1 tablespoon chopped fresh thyme
• 2 cups heavy cream
• 1 cup whole milk
• 1 pinch cayenne
• 3/4 cup shredded Gruyere cheese
• 3/4 cup shredded cheddar cheese
• 6 russet or yukon gold potatoes, cut into 1/8-inch-thick slices