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 mxture 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 4F.
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
Serve with tartar sauce.