Fudge filling is a cooked sugar, butter, cream, and chocolate mixture used to fill or top cakes, pastries, and confections, sharing fudge's soft-ball-stage cooking method (about 234-240°F / 112-116°C) but formulated to stay soft and spreadable rather than being cut into set pieces. It differs from a chocolate ganache, which is simply melted chocolate and cream with no sugar-cooking stage, in that fudge filling relies on controlled sugar crystallization for its dense, smooth texture. It is used to fill cakes such as Boston cream pie, sandwich cookies, and doughnuts, and as a topping for cupcakes; overcooking makes it dry and crumbly, while undercooking leaves it runny and unset.