plus 2 tablespoons for topping
1 1/2 teaspoons kosher salt, divided
1 teaspoon freshly ground black pepper
2 teaspoons fresh thyme leaves, chopped (or 1 teaspoon dried thyme)
3 pounds russet or Yukon Gold potatoes, peeled (if desired) and thinly sliced
1 tablespoon unsalted butter or cooking spray, for greasing the glass casserole dish
Directions
Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch glass casserole dish with 1 tablespoon butter or cooking spray. Set aside.
Caramelize the onions: In a large skillet, melt 2 tablespoons
