Pick through the crab to remove any shell bits, then gently pat it dry.
Whisk mayonnaise, beaten egg, Dijon, Worcestershire, lemon juice, Old Bay, salt, and pepper in a large bowl.
Fold in the crab, parsley, and celery until just combined; keep the crab in large flakes.
Sprinkle in the panko and fold gently until the mixture barely holds together.
Shape into 8 patties, pressing lightly. Chill 10–15 minutes to firm up.
Heat oil and butter in a large skillet over medium heat until shimmering.
Pan-fry crab cakes 3–4 minutes per side until deeply golden and heated through.
Drain briefly on paper towels and serve hot with a squeeze of lemon, if desired.