How to Make It
Preheat oven to 500°F with the rack in upper third. Toss potatoes with butter, thyme, salt and pepper. Transfer to a 13-by-9 inch metal baking dish and arrange in a single layer. (Don’t use a glass pan, which can burst under such high heat.)
Bake 15 minutes, flip the potatoes, then bake 15 minutes more. Remove the dish from the oven and add chicken stock and garlic cloves. Return to the oven until most of the stock is absorbed, about 15 minutes more. Transfer to a serving platter and pour any remaining liquid in the pan overtop. Serve warm.