1-First, preheat your oven to 350°F (177°C) and line two standard cupcake pans with liners to make baking seamless. Sift together 1 cup plus 2 tablespoons all-purpose flour, 3/4 cup unsweetened cocoa powder, 3/4 teaspoon salt, 1 and 1/8 teaspoon baking soda, and 1/2 teaspoon baking powder; set this mixture aside for later. In a large bowl, beat 3/4 cup unsalted butter (room temperature) and 1 cup plus 2 tablespoons granulated sugar until pale and fluffy, which takes about 5 minutes, for a light batter base.

2-Next, add 2 large eggs (room temperature) one at a time, blending after each to incorporate fully. Combine 2 and 1/2 teaspoons pure vanilla extract with 2 and 1/2 teaspoons instant coffee granules, then mix this into 6 tablespoons sour cream (room temperature) before adding it to the batter for extra flavor depth. Alternate adding the dry ingredients and 1 cup plus 2 tablespoons buttermilk (room temperature) to the batter, mixing gently after each addition to keep the texture perfect. Spoon one tablespoon of batter into each liner, add a frozen peanut butter cup, and cover with more batter until two-thirds full.

3-Baking and Filling Steps: Bake the cupcakes for 18-20 minutes until a toothpick inserted comes out clean, then cool them in the pans for 5 minutes before transferring to racks to cool completely. For the peanut butter ganache filling, microwave 1 cup peanut butter chips and 1/3 cup heavy cream in 30-second intervals until steaming hot (about 1 minute), then stir until a thick ganache forms. Once the cupcakes are cool, core each one and fill the centers with this ganache.

4-For the chocolate buttercream, beat 1 cup unsalted butter (softened) and 1/8 teaspoon salt until fluffy. Add half of 3 cups powdered sugar (sifted) and 1/4 cup unsweetened cocoa powder (sifted), mixing on low speed, then incorporate 8 oz melted and cooled semi-sweet chocolate chips and 2 teaspoons pure vanilla extract. Gradually add the remaining powdered sugar and 4-6 tablespoons heavy cream or milk as needed, whipping on medium-high until light and fluffy.

5-Similarly, for peanut butter buttercream, beat 1/2 cup unsalted butter (softened), 1/2 cup creamy peanut butter, and 1/8 teaspoon salt until fluffy. Add half of 3 cups powdered sugar (sifted) on low speed, then mix in 6 tablespoons heavy whipping cream and 1 and 1/2 teaspoons pure vanilla extract. Finish with the remaining powdered sugar and adjust with cream for the right consistency, whipping until fluffy. To assemble, use a large piping bag divided into two sections to pipe chocolate frosting on one side and peanut butter frosting on the other, swirling them together, and garnish each with a peanut butter cup.