Prepare cake batter according to package directions; fold in 2/3 cup coconut. Pour into two greased and floured 9-in. round baking pans. Bake at 350° for 25-30 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a microwave, melt white chocolate and cream at 70% power for 1 minute; stir. Microwave at additional 10- to 20-second intervals, stirring until smooth.Cool to room temperature.
In a small bowl, combine jam and 1 cup coconut. Spread over one cake layer; top with second layer.
In a small bowl, beat butter until fluffy. Add confectioners’ sugar; beat until smooth. gradually beat in white chocolate mixture. Spread over top and sides of cake. Toast remaining coconut; press over top and sides of cake.