1 (18.5 ounce) package yellow cake mix
1 cup vegetable oil
3 eggs, beaten
1 (3 ounce) package instant vanilla pudding mix
1 (3 ounce) package instant chocolate pudding mix
1/3 cup milk chocolate syrup
1 1/2 cups white sugar
1 teaspoon vanilla extract
1 cup butter
1 cup white sugar
1 teaspoon vanilla extract
1 teaspoon orange zest
1 cup butter, softened
1 cup white sugar
1 cup confectioners' sugar
Preheat oven to 300 degrees F (150 degrees C). Grease two 9-inch round cake pans or two 9 inch round pans.
In a large bowl, combine cake mix, vegetable oil and eggs. Beat until blended; stir in pudding mixture, chocolate pudding mix, custard and milk chocolate syrup. Beat for 1 minute.
Pour batter into prepared pans.
Bake in the preheated oven for 50 to 60 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool completely.
While the cake is cooling, prepare the frosting. Sift together the confectioners' sugar, butter, white sugar and brown sugar. Add the butter mixture and lemon zest; mix until smooth. Spread frosting over the cake. Chill cake while serving warm.