Preheat oven 350F. Coat 15 x 10 x 1-inch baking pan with nonstick cooking spray.
Line pan with waxed paper and coat with nonstick cooking spray. Sprinkle pecans and coconut evenly over paper.
In mixing bowl, prepare cake mix with water, oil, eggs and egg whites according to directions on box. Spread batter carefully and evenly over pecans and coconut.
Bake 15 to 18 minutes or until top springs back when done. Let cool.
To prepare icing: In mixing bowl, beat together butter, cocoa, confectioners sugar, vanilla and coconut extracts, adding milk gradually until creamy consistency. Spread over cooled cake. Cut into 60 squares.