Prepare the cake according to package directions. Set aside to cool. To make coconut filling, mix egg yolks, sugar, and salt in a medium bowl; beat in butter, then gradually beat cream or evaporated milk and vanilla into mixture. Pour into a medium saucepan and cook over low heat, stirring continuously until mixture is bubbly and just begins to thicken, 15 to 20 minutes. Pour into bowl and cool to room temperature. Stir in pecans and coconut. To assemble, spread 1 to 1 1/2 cups of coconut filling between layers and sprinkle with chocolate chips and coarsely chopped cherries. Spread remaining coconut filling over top and sides of cake and sprinkle top with cherries and chocolate chips.