In a food processor, pulse cornflakes until ground coarse and spread in a shallow baking pan.

In a large bowl, whisk together mayonnaise, mustard, Old Bay seasoning, cayenne and yolks and add crab meat and salt and pepper to taste, tossing mixture gently but thoroughly.

With a 1/4 cup measure, form crab miguel into slightly flattened rounds about 2 1/2 inches wide and 3/4 inch thick and gently coat crab cakes with cornflakes, transferring as coated to a wax-paper-lined baking sheet. Chill crab cakes, covered with plastic wrap, at least 2 hours and up to 4 hours.

Preheat oven to 400F.

Transfer crab cakes to a large baking sheet. Put about 1/2 teaspoon butter on each crab cake and bake in the middle of the oven until crisp and cooked through, about 15 minutes.

Serve with tartar sauce.