Preheat the oven to 350°. Line 12 cupcake tins with paper cupcake liners.
In a medium bowl, whisk the hot coffee and cocoa together until smooth. Set aside.
In a large mixing bowl, add the sugar, flour, baking powder, baking soda, and salt. Using a whisk, blend and sift the ingredients together.
Add the eggs, milk, oil, vanilla, and the cocoa mixture to the dry ingredients. Mix on low speed for 30 seconds until the dry ingredients are moist. Increase the speed to medium and beat for 1 minute. Scrape down the sides and beat for another minute. The batter will be thin.
Fill the cupcake tins just over half full. Bake 15 to 20 minutes or until a toothpick inserted in the middle comes out clean.
Let cool in the cupcake tins for 5 to 10 minutes before removing them to a cooling rack to cool completely.
Peanut Butter Cream Cheese Frosting
Combine the cream cheese, peanut butter and butter in a medium-size mixing bowl. Beat with an electric mixer on medium-high speed for 2 to 3 minutes or until smooth. Stop the mixer once or twice to scrape down the sides of the bowl.
Add the milk, vanilla and salt. Mix on medium speed for 1 minute. Scrape down the sides of the bowl.
Add the powdered sugar and blend on very low speed or by hand until the sugar is absorbed. If you start the mixer too fast you will create a sugar-dust cloud in the kitchen.
Increase the speed to medium-high and blend 2 to 3 minutes until smooth. Stop the mixer partway through to scrape down the sides.
Fill and frost the cupcakes:
Fill the cupcakes: You can do this easily by filling a pastry bag with frosting and pushing the tip partway down into the cupcake. Gently squeeze the bag so that frosting gets pushed into the center of the cupcake. If you see the cupcake start to bulge then stop squeezing. Another way to fill the cupcakes is to cut a small core out of the center of each cupcake and pipe the frosting inside.
Spread the frosting onto the cupcakes with a knife or use a decorator bag or a ziplock bag to pipe it on.
Garnish with a mini Reese’s peanut butter cup.
Notes
Use room temperature ingredients: Let the eggs, milk, cream cheese, and butter sit out before starting so everything mixes smoothly.The batter will be thin: Don’t worry, that is normal for this recipe. Fill liners just over halfway: This batter rises well, so avoid overfilling to prevent spillover.Cool completely before filling and frosting: Warm cupcakes will melt the frosting and make a mess.Use a standard creamy peanut butter: Natural peanut butter can separate and affect the texture of the frosting.Start checking early for doneness: Check at 15 minutes to avoid overbaking.Store in the refrigerator: Because of the cream cheese frosting, keep the cupcakes chilled, then let them sit at room temp before serving.