Preheat oven to 350 and line muffin tins with cupcake liners.
In the bowl of a stand mixer, combine egg whites, egg, oil, buttermilk, sour cream and zest at low speed.
Add in the cake mix and mix on medium speed, then fold in cranberries.
Use a medium cookie scoop to fill cupcake liners 3/4 full.
Bake for 10 minutes (14- 16 for standard size), until toothpick inserted comes out clean.
Allow to cool in the pan for 1 minute, then remove to a wire rack to cool completely.
While the cupcakes are cooling make the ganache by melting the white chocolate chips and heavy cream together in a double boiler or in the microwave for 30 seconds at a time, stirring after each time until almost melted, then stir until completely melted.
Be careful not to heat to long or the chocolate will burn.
Invert the cooled cupcakes, one at a time and dip into the ganache.
Place back on the wire rack and allow the ganache to set.
Meanwhile, in the (cleaned) bowl of your stand mixer,beat cream cheese and butter at med-high speed for 4 minutes.
Add in the pudding mix, vanilla extract and powdered sugar and mix at medium-low speed until well combined.
Add up to an additional 1 cup of powdered sugar, 1/4 cup at a time, if frosting is too thin.
Use a spatula to scoop the frosting into your piping bag with your preferred decorating tip, and pipe away.
Top with red sugar sprinkles for an extra festive display.