In a medium bowl, combine the crab meat and the Panko bread crumbs. Stir in the beaten egg, grated onion, mayonnaise, mustard, worcestershire sauce, and Old Bay seasoning. Lightly mix all ingredients, then form into 8 round (fairly flat) crab cakes.
Heat the butter in a skillet over medium heat. Fry the crab cakes on each side until they are crusty and golden brown. Serve warm with either a roumalade sauce, tartar sauce, or cocktail sauce (or if you prefer, just plain, with a little lemon juice squeezed on top)