1Blend chocolate cake mix according to package instructions, with eggs, oil and water; set batter aside. In a separate bowl, prepare white cake mix according to package instructions, with egg whites, oil and water.
2Using an ice cream scooper, pour two scoops of the White Cake batter into a Bundt cake pan. Next pour 2 scoops of chocolate batter on top of White. Continue to alternate between White and chocolate batters until Bundt pan is filled.
Bake according to package directions. Cool as instructed and remove from pan to cooling rack.
Place the chocolate chips into a medium bowl. Heat the cream in a small saucepan over medium heat. Bring just to a boil, watching very carefully because if it boils for a few seconds, it will boil out of the pot.
When the cream has come to a boil, pour over the chopped chocolate, and whisk until smooth. Stir in a little rum, if desired. Allow the ganache to cool slightly before pouring over cake.
Start at the center of the cake and work outward. For a fluffy frosting or chocolate filling, allow mixture to cool until thick, then whip with a whisk until light and fluffy.