Pre-heat oven to 350°. Line a muffin tin with non-stick/parchment cupcake liners.
Whisk together all dry cupcake ingredients in a large bowl. Set aside.
Whisk together all wet ingredients, then add to dry ingredients and mix until just combined.
Fill cupcake liners 1/2 to 3/4 full with batter. Bake at 350° for 18-21 minutes or until a toothpick inserted into the center comes out clean. Remove to cool.
Using a hand held mixer or stand mixer with paddle attachment, beat the butter on medium until creamy, about 2 minutes. Add powdered sugar, heavy cream, bourbon, and vanilla extract.
Beat on low speed for 30 seconds, then increase to medium-high speed and beat for 2 full minutes. Scoop into a piping bag and pipe onto cooled cupcakes.