Heat oven to 400Â°.
Grease square pan, 8x8x2 inches.
Stir together coconut, nuts, 1/2 cup sugar and 1 tablespoon of the melted butter; set aside.
Mix baking mix, 1/4 cup sugar, remaining melted butter, the egg and milk.
Beat vigorously 1/2 minute.
Pour into pan.
Spoon chocolate over batter; with knife, cut through batter several times for a marbled effect.
Sprinkle coconut mixture evenly over top.
Bake 20 to 25 minutes.