In a medium mixing bowl, combine flour, cocoa powder, sugar, baking soda, baking powder, salt and whisk together.
In a smaller bowl, combine oil, egg, greek yogurt, and stir to combine. Pour wet mixture into dry mixture and mix until fully incorporated. Add cooled brewed coffee last, and stir to combine.
Prepare mini muffin pan with cooking spray or mini cupcake wrappers, and fill each cup 2/3 of the way.
Bake at 350 for 11-13 minutes, until a toothpick comes out clean.
In a stand mixer or in a mixing bowl with a hand mixer, beat Smart Balance for 60 seconds until light and fluffy. Add powdered sugar 1/2 cup at a time until fully incorporated. Add Baileys, and mix on medium speed until you have a uniform, fluffy frosting. If too dry, add more Baileys 1/4 tsp at a time. If too liquid, add powdered sugar 1 tbsp at a time.
Let cupcakes cool completely before frosting. Frost each cupcake with roughly 1 tsp of frosting and enjoy! Store in the fridge for up to 4 days.