Skillet Scalloped Potatoes with Chive Butter

Preheat oven to 400 degrees F. In a large cast iron skillet over medium-high heat, melt butter and add garlic, onion, and thyme. Cook until mixture is softened, 3 to 5 minutes. Add 1 1/2 teaspoon salt, 1/2 teaspoon pepper, heavy cream, and chicken stock and bring to a boil. Turn off heat and mix in chives and half of fontina. Add potatoes to skillet and arrange in any pattern, keeping slices vertical to ensure even cooking. Bake 40 minutes. Sprinkle remaining fontina all over and bake until cheese is melty and crust is golden brown, 10 minutes more. Garnish with chives and serve immediately.