Classic Potato & Caramelized Onion, Gruyère Gratin

Ingredients

• While the onions cook, prep the potatoes. Use a sharp peeler to peel the potatoes. Rinse off, then slice into 1/8” thick slices using a handheld mandoline.
• Preheat the oven to 400° F.
• Top the final layer of potatoes with the remaining onions, then sauce, and finally sprinkle with the reserved 1/4 cup of cheese.
• Garnish with additional fresh stems of thyme, and serve while hot.
• 2 tablespoons butter
• 2 medium sweet onions, sliced pole to pole
• 1 teaspoon fresh thyme leaves
• 2 lbs Russet potatoes (about 2-3 medium to large potatoes), washed, peeled, and thinly sliced with a mandoline
• 3 cloves garlic, minced
• 4 tablespoons butter
• 1/4 cup all-purpose flour
• 3 cups whole milk
• 1-1/2 teaspoons Kosher salt
• 1/4 teaspoon black pepper
• 2 cup grated Gruyère, 1/4 cup reserved for topping the gratin