1In a large bowl, whisk together 1/4 cup of the mayonnaise, the egg, mustard, Worcestershire, hot sauce, Old Bay, parsley and green onions until smooth.
2Add 1/3 cup of the panko and the crab meat. Fold with a rubber spatula just until combined, keeping the lumps as intact as you can. Season with a few grinds of pepper.
3Shape the mixture into patties about 3 inches wide and 1 inch thick, pressing just enough that they hold. Dust both sides lightly with the remaining panko, set them on a plate, and chill for at least 30 minutes so they firm up.
4While the cakes chill, stir the remaining 1/4 cup mayonnaise with the relish and a squeeze of lemon juice from half the lemon. Add a pinch of pepper if you like. Refrigerate until serving.
5Heat the butter and vegetable oil in a large skillet over medium heat until the butter foams. Lay in the cakes without crowding, working in batches if needed.
6Cook without moving them for 4 to 5 minutes, until the underside is deep golden. Flip carefully with a wide spatula and cook 3 to 4 minutes more, until browned and hot through.
7Serve right away with the sauce and lemon wedges.
8Let the leftover fat in the skillet cool completely in the pan. Because it carries butter and crumbs, spoon it into a sealed container and discard it with the trash. Never pour it down the drain, since it hardens in the pipe.