Preheat oven to 375F. Prepare your pan by lining with cupcake liners and putting a peanut butter cup in each. Set aside.
In a medium bowl, whisk together 1 ½ cups flour, ½ cup cocoa powder, 1 teaspoon baking soda and ¼ teaspoon salt. Set aside.
In another bowl, stir together your ½ cup coffee and ½ cup buttermilk. Set aside.
Using an electric hand mixer or a stand mixer fitted with the paddle attachment, cream ½ cup butter and 1 ½ cups sugar until light and fluffy.
Add eggs one at a time making sure each one is incorporated well.
Add 2 teaspoons of vanilla and continue to stir until combined. Remember to scrape the sides and the bottom of your bowl.
Add a third of your flour mixture into your butter mixture and mix well. Then add half of your buttermilk/coffee mixture. Add in another third of your flour, the rest of your buttermilk and finally the rest of your flour. Make sure to beat well after each addition.
Pour the batter evenly into your baking cups until they are about ⅔ full.
Bake for 10-20 minutes or until a toothpick inserted in the centre comes out clean (my mini cupcakes were done in 10 minutes while my regular cupcakes were done in 15).
Cool in the pans for 10 minutes then transfer to a wire rack to cool completely before frosting.
Peanut Butter Frosting:
Using a handheld electric mixer or a stand mixer fitted with the paddle attachment, cream 2 cups peanut butter, ½ cup butter and 2 teaspoons vanilla until smooth.
Add ¼ teaspoon salt and ¼ cup heavy cream and continue beating until well combined.
Gradually add the 2 cups confectioner's sugar (about ½ cup at a time) and beat until you get a smooth and fluffy consistency.
Reese's Minis work best for mini cupcakes, and the miniatures work best for standard/regular-sized cupcakes
This recipe yields 24 standard size or 48 mini cupcakes.