Scalloped Potatoes

Ingredients

• 3 Tablespoons Unsalted Butter
• 1 Onion, small yellow, peeled and thinly sliced
• 4 garlic cloves large, minced
• 3 Tablespoons all-purpose flour
• 1 cup Chicken or vegetable stock
• 2 cups milk, 2% preferably
• 1 teaspoon Kosher salt
• 1/2 teaspoon black pepper
• 2 teaspoons fresh thyme leaves, divided
• 4lbs Yukon Gold Potatoes, sliced into 1/8-inch rounds, peeling optional
• 1 1/2 cups Brennan's Sharp Cheddar or Extra Sharp Cheddar, grated and divided
• 1/2 cup American Grana or Parmesan, freshly grated