3 pounds potatoes (peeled and sliced 1/8 inch thick)
Preheat oven to 400F and lightly spray a 13×9 casserole dish with cooking spray.
Place 2 tablespoons of olive oil in a large skillet over medium heat, add the onions and season with a ½ teaspoon salt, and ¼ teaspoon pepper. Cook stirring frequently until onions are browned. Add the minced garlic and ¼ teaspoon thyme and continue to cook until fragrant. Stir in ¼ chicken broth and continue cooking until broth is evaporated. Remove from heat and set aside.
In a large bowl while onions are cooking mix together the Romano cheese, 3 tablespoons olive oil, panko bread crumbs, and 1/2 teaspoon pepper. Set aside.
Place the sliced potatoes in a large bowl and toss them with 3 tablespoons olive oil, 1 teaspoon salt, 1/2 teaspoon pepper, and remaining 1/4 teaspoon thyme.
Spread ½ of the sliced potatoes in the casserole dish and distribute the onion mixture evenly over the top followed by the other half of the potatoes. Pour the remaining broth over the potatoes, tightly cover with aluminum foil and bake for 1 hour.
Remove the casserole from the oven, remove the aluminum foil, and sprinkle the Romano cheese mixture over the top. Bake uncovered for an additional 15 – 20 or until cheese mixture is browned.