Preheat oven to 350 degrees F and prepare a cupcake pan with paper cupcake liners.
In a large mixer bowl, cream the butter and sugars together until light and creamy, about 3-4 minutes. Add the sour cream and vanilla extract and mix until well combined.
Add the egg whites, one at a time, and mix until combined. Scrape down the sides of the bowl as needed.
In a small bowl, whisk together the baking powder, cinnamon and salt. In a small measuring cup, whisk together the milk and water. Alternately add the flour and milk to the batter, mixing well after each addition, beginning and ending with the flour. Mix until well incorporated.
Fill the cupcake liners about half full with batter. Bake the cupcakes for 15-17 minutes or until a toothpick inserted into the center comes out clean.
Let cupcakes cool in the pan for 2-3 minutes before transferring them to a cooling rack to cool completely.
For the Frosting
Beat the mascarpone cheese, powdered sugar and vanilla extract together on medium-low speed until smooth. Be careful not to over mix as the mascarpone can get thin and watery.
Place frosting into a piping bag fitted with Wilton Tip 1M, 2D, or Ateco 844. Frost the tops of the cupcakes, then garnish with mini chocolate chips and a light dusting of powdered sugar.