Pick the crabmeat from the king crab; remove any shell or cartilage that may be in the crabmeat. Lightly squeeze some of the water from the crab and discard. Place the crabmeat to one side. Open the lump crabmeat and squeeze some of the water from the crab and discard.
Place the crabmeats into a bowl and mix with the mayonnaise, lemon zest, Old Bay Spice, mustard, spring onions, egg, mashed potato and the fresh breadcrumbs, season to taste. Form into 3 ounce cakes, shallow fry in olive oil and foaming butter until golden brown on both sides.