WHITE / RAINBOW BUNDT CAKE – 3/4 cup buttermilk , room temperature – 2/3 cup sour cream , room temperature – 4 egg whites , room temperature – 1/3 cup vegetable oil – 1 Tablespoon vanilla – 1 15.25oz Box Cake White Mix, I used Duncan Hines for the best taste and texture, but any other brand will be similar. – rainbow gel colors (red, orange, yellow, green, blue, purple) WHITE CHOCOLATE GANACHE DRIP – 1 cup "bright white" chocolate candy melts , I used Wilton brand, but I also love Sweet Tooth Fairy chocolate melt – 1/4 cup heavy cream EXTRAS – 1/2 cup rainbow jimmies/sprinkle