Preheat your oven to 350°F (175°C) and line two muffin pans with paper liners.

In a large mixing bowl, combine the cake mix, egg whites, water, oil, and pudding mix. Beat on medium for 2 minutes.

Distribute the batter among the muffin cups, filling each about 3/4 full. Bake for 15-18 minutes.

Allow the cupcakes to cool in the pans for a few minutes, then transfer to a wire rack to cool completely.

Melt the peppermint baking chips with some heavy cream in the microwave until smooth. Whip the remaining cream until soft peaks form and fold in the melted mixture.

Core each cooled cupcake to create a well for the mousse.

Fill each cored cupcake with peppermint mousse using a piping bag or spoon.

Melt white chocolate chips with a bit of heavy cream. Beat softened butter, then mix in chocolate, cream, vanilla, and sugar to create frosting.

Frost the cupcakes and garnish with crushed candy canes and peppermint bark if desired.

Store leftovers in an airtight container in the fridge for up to 4-5 days or at room temperature for 2-3 days.