Step 1: In a large bowl, gently combine the mayonnaise, beaten egg, Dijon mustard, Worcestershire sauce, Old Bay seasoning, 2 tablespoons of the chopped parsley, salt, and pepper. Mix until just combined.
Step 2: Add the jumbo lump crab meat and panko breadcrumbs to the bowl. Very gently fold the ingredients together using a rubber spatula or your hands, being careful not to break up the large crab lumps. The mixture should just come together.
Step 3: Divide the mixture into 8 equal portions and gently form them into patties, about 1-inch thick. Avoid pressing too firmly. Place the formed crab cakes on a plate or baking sheet lined with parchment paper and chill in the refrigerator for at least 30 minutes to help them firm up.
Step 4: Heat the olive oil and 2 tablespoons unsalted butter in a large non-stick skillet over medium-high heat until the butter is melted and sizzling. Carefully place 4 crab cakes into the hot skillet, ensuring not to overcrowd the pan. Cook for 3-5 minutes per side, until golden brown and heated through. Repeat with the remaining crab cakes, adding more oil and butter if needed.
Step 5: While the crab cakes are cooking or immediately after, prepare the lemon butter sauce. In a small saucepan, melt 1/2 cup unsalted butter over medium heat. Stir in the fresh lemon juice, minced garlic, remaining 2 tablespoons of fresh parsley, and optional red pepper flakes. Season with a pinch of salt to taste. Simmer for 1-2 minutes, allowing the flavors to meld.
Step 6: Serve the hot crab cakes immediately, drizzled generously with the warm lemon butter sauce. Garnish with additional fresh parsley if desired. Enjoy!