6.
Adjust oven rack to 6 inches below broiler element and preheat broiler to high. Heat oil and butter in a large cast iron skillet over medium heat until foaming subsides. Add crab cakes, breaded side down and cook, swirling occasionally, for 3 minutes. Carefully peel off foil from each cake using your fingertips, without lifting the cakes. Discard the foil. Continue cooking, swirling pan occasionally until underside of crab cakes is light golden brown, about 2 minutes longer (check underneath with a thin flexible metal spatula, but be careful not to break crab cakes, they will be fragile)