Preheat oven to 350°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, baking soda, and salt, stirring with a whisk.
Place sugars and butter in a large bowl; beat with a mixer at medium speed for 3 minutes or until well combined. Add maple flavoring and egg; beat until combined. Add flour mixture; stir until well combined. Stir in pecans. Spread mixture evenly in a 9-inch cast-iron skillet. Bake at 350° for 30 minutes. Cool in pan 10 minutes on a wire rack.
Remove from pan, and drizzle with melted chocolate. Cool completely.