Preheat the oven to 350°F and line a 12 cup pan with cupcake liners.
Finely chop the fresh mint and add to the granulated sugar along with the lime zest. Then use your fingers to gently massage the mint and lime zest into the sugar. [This is optional, but helps infuse the oils into the sugar for more flavor.]
Whisk the cake flour, baking powder, and salt together in a large bowl.
In a separate bowl, whisk the melted butter and flavored sugar.
Add in the eggs, vanilla, mint extract, and lime juice and whisk until fully combined.
Stir in about half of the flour mixture. Then stir in the yogurt, white rum, and the rest of the flour mixture and mix until fully combined. The batter will be thick.
Pour about ¼ cup of batter into each cupcake liner (they should be about halfway full).
Bake at 350°F for 18-22 minutes or until a cake tester comes out clean.
Remove from cupcake pan and let cool on wire rack.
Let cupcakes cool completely before frosting.
Optional: pour 1 tablespoon of white rum into a small bowl and using a pastry brush, lightly brush the tops of the cupcakes with rum before frosting.
Frosting
While the cupcakes are cooling, make the frosting.
In a stand mixer fitted with the paddle attachment, cream together the softened butter and cream cheese until completely smooth. Then add in the powdered sugar and beat on slow until combined.
Slowly add in the lime juice, mint extract, rum, and salt until fully combined. Then beat the buttercream for 3-4 minutes on high speed until light and fluffy.
Frost cooled mojito cupcakes, then garnish with fresh mint, lime slices, and, lime zest.
Notes
These cupcakes will last in the fridge for up to 3 days. However, they taste best when served at room temperature! I like to let them sit at room temperature for about an hour before serving. But I recommend waiting to top with mint, lime zest, and lime slices until immediately before serving!There is rum in the frosting, so these cupcakes should only be served to people over the age of 21.To make these cupcakes non-alcoholic, instead of using rum in the cupcakes and frosting, you can substitute rum extract. The flavor won't be quite the same but they're still good! Use 2 teaspoons of rum extract in the cupcake batter and 1 teaspoon of rum extract in the frosting.