Place 4 tablespoons of the butter in a small microwavable bowl. Microwave on HIGH until melted, about 30 seconds. Gently stir together melted butter, crabmeat, egg, chives, lemon zest, 1 tablespoon of the lemon juice, 3/4 cup of the panko, 1 1/2 teaspoons of the salt, and 1/2 teaspoon of the pepper in a medium bowl. Shape into 24 (1 1/2-inch) cakes. Sprinkle remaining 3/4 cup panko on a large plate. Transfer cakes, in batches, to plate; dredge both sides in panko, pressing to adhere. Place cakes on a baking sheet lined with parchment paper. Cover; chill 15 minutes or up to 8 hours.

Stir together mayonnaise, hot sauce, Cajun seasoning, and remaining 1/2 tablespoon lemon juice, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a bowl; set aside. 

Heat 2 tablespoons each of the butter and oil in a large nonstick skillet over medium. Add 12 cakes; cook until golden brown and heated through, 3 to 4 minutes per side. Transfer cakes to a plate; tent with foil to keep warm. Wipe skillet clean. Repeat with remaining 2 tablespoons butter, 2 tablespoons oil, and 12 cakes.

Place each crab cake on a lettuce leaf. Top each with about 1 teaspoon of the sauce. Garnish with chives and lemon wedges. Serve immediately.