For the Mocha Cupcakes:
- 6 tablespoons unsalted butter, room temperature
- ¾ cup sugar
- 6 tablespoons sour cream, room temperature
- ½ teaspoon vanilla extract
- 3 large egg whites, room temperature
- 1 ¼ cups all-purpose flour
- 2 teaspoons baking powder
- ¼ teaspoon salt
- 2 tablespoons hot water
- 3 tablespoons instant espresso coffee powder
- 6 tablespoons milk, room temperature
For the Caramel Frosting:
- ½ cup salted butter
- ½ cup shortening
- 4 cups powdered sugar
- 5 – 6 tablespoons caramel sauce
- 1 – 2 tablespoons water or milk