In a medium bowl whisk together the flour, sugar, baking powder, baking soda, and salt.
Add the buttermilk, milk, vanilla, and oil to the dry ingredients and beat with the paddle attachment of a stand mixer or a hand mixer until just fully combined. In a separate bowl whip the egg whites until you get medium-stiff peaks and gently fold into the batter.
Scoop the batter into the cupcake liners until they are 2/3 of the way full. Bake for 20-22 minutes, until a toothpick, comes out clean and the tops of the cupcakes bounce back when lightly pressed. Let the cupcakes cool completely before frosting.
Before starting your frosting, prep by placing the bowl and whisking in the freezer for at least 20 minutes. This will help your frosting whip up stiff.
Once chilled, place the mascarpone in the bowl and use the whisk to beat on medium speed. Add the orange zest, vanilla, and powdered sugar. Scrape down the sides and beat until fully combined, about 1 minute. It will be quite soft at this stage.
With the mixer on medium-high speed, slowly add in the whipping cream. Once incorporated (it will be very liquidy), scrape down the sides and then beat on high for 1-3 minutes, until light and fluffy. If the frosting is still quite loose, try chilling it for 5-10 minutes and then beat again. The goal is to achieve a light whipped cream frosting that is stabilized by the mascarpone.
Use immediately to frost your cupcakes. Sprinkle with mini chocolate chips. Chill until ready to serve.