Cook the Juicy Lucys. Heat 1 tablespoon vegetable oil in a large cast iron skillet or frying pan over medium heat until shimmering, 3 to 4 minutes. If using a 10-inch pan, place 2 patties in the pan; if using a 12-inch or larger, add all 4 patties. Cook undisturbed (do not press down on the patties) until dark golden-brown on the bottom, about 4 minutes. Using a spatula, flip the patties and cook until the second side is dark golden-brown and the patties are cooked through, about 4 minutes.