Spread crab on a plate and remove any shell bits. Pat dry with paper towels.
Whisk mayonnaise, beaten egg, Dijon, Worcestershire, lemon juice, Old Bay, salt, and pepper in a bowl.
Stir in parsley, green onion, and bell pepper until evenly distributed.
Gently fold in crab and then panko. Mix just until it holds together; avoid breaking the lumps.
Chill the mixture 10–15 minutes to firm up for shaping.
Form 8 patties about 2.5 to 3 inches wide. Press lightly to compact.
Heat oil and butter in a large skillet over medium heat until shimmering.
Cook crab cakes 3–4 minutes per side, in batches if needed, until deep golden and heated through.
Drain briefly on a rack or paper towels. Serve hot with lemon wedges or your favorite sauce.