Preheat the oven to 350 degrees F. Line mini cupcake pans with paper liners (for a total of 36 mini cupcakes).
For the mimosa orange cupcake: In a medium bowl, combine the flour, baking powder and salt. Set aside.
Using a stand mixer with the paddle attachment, cream the butter and sugar on medium speed. Mix in the egg. In two parts, alternate adding the milk with the dry ingredients. Add the vanilla and beat until well blended. Fold in the champagne and orange zest and juice.
For the white chocolate cheesecake: Mix together the cream cheese, sugar, vanilla and egg in a stand mixer with the whisk attachment until fluffy and smooth, about 3 minutes.
In a double boiler, melt the white baking chocolate. Mix into the cheesecake batter until combined.
Layer the cupcake liners with the mimosa orange cupcake batter first. Add 2 white chocolate chips to each, and then top with a layer of the white chocolate cheesecake batter. Fill the liners with both batters about three-quarters full because the cupcakes will rise. (Depending on your layering technique, you may have more of one batter than the other. You can always make straight cupcakes or cheesecakes with the extra batter.)
Bake about 18 minutes. Set aside to cool completely.
For the champagne buttercream frosting: Beat the butter in a stand mixer until light and fluffy. Add the confectioners' sugar 1 cup at a time, beating after each addition. Add the champagne, vanilla and salt and beat until creamy.
Put the frosting in a piping bag and frost the cooled cupcakes generously.
Don't overdo the champagne, which could cause runny batter and the frosting to break apart.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.