Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well combined.
In a separate bowl, mix the melted butter, eggs, milk, and vanilla extract. Whisk until smooth.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Be careful not to overmix.
Fold in the semi-sweet chocolate chips until evenly distributed throughout the batter.
Fill each cupcake liner about 2/3 full with the batter.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
While the cupcakes are baking, prepare the peanut butter frosting. In a bowl, mix the creamy peanut butter and powdered sugar until smooth and creamy.
Once the cupcakes are done, let them cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
Once cooled, top each cupcake generously with the peanut butter frosting. Optionally, drizzle with additional melted chocolate for an extra touch of decadence.
Notes
For a delightful finishing touch, sprinkle a few chocolate chips on top of the frosted cupcakes and place a mini peanut butter cup on each one for added flavor and style.