1. Preheat the oven to 350°F (176°C) and prepare a cupcake pan with cupcake liners.
2. In a large mixing bowl, cream the butter and sugar together until light in color and fluffy, about 3-4 minutes. Do not skimp on the amount of creaming time.
3. Add sour cream and vanilla extract and mix until well combined.
4. Add egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Combine dry ingredients in a separate bowl, then combine the ginger beer and vodka in a small measuring cup.
6. Add half of the dry ingredients to the batter and mix until well combined. Add the ginger beer mixture and mix until well combined. Add remaining dry ingredients and mix until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
7. Fill the cupcake liners about halfway. Bake for 15-17 minutes, or until a toothpick inserted comes out with a few crumbs.
8. Remove cupcakes from oven and allow to cool for 2-3 minutes, then remove to cooling rack to finish cooling.
9. To make the frosting, combine the butter and shortening with a mixer until smooth.
10. Add about half of the powdered sugar and mix until smooth and well combined.
11. Add the ginger and mix until combined.
12. Add 3 tablespoons of ginger beer to the frosting and mix until well combined.
13. Add the remaining powdered sugar and mix until smooth.
14. Add the lime zest and mix until smooth. Add additional ginger beer as needed to get the right consistency.
15. Pipe the frosting onto the cupcakes. I used Ateco tip 808.