Crème Caramel Renversée (Upside-Down Caramel Custard)

The velvety texture of a well-made crème caramel comes from gentle heat that leaves the custard free of bubbles; it’s taken from the oven just at the moment the center has crossed over from thickened to set. It contains no flour, a crutch that prevents the liquid from separating in case of overcooking. Farmyard eggs have more flavor and make a slightly …