For the Cupcake:

1. 1. Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
2. 2. In a large mixing bowl, whisk together flour, cocoa powder, baking powder, and sugar until well combined.
3. 3. In another bowl, beat the eggs, milk, and vegetable oil until smooth. Add this mixture to the dry ingredients and stir until just combined.
4. 4. Spoon batter into each cupcake liner until about two-thirds full. For an extra surprise, add a dollop of peanut butter into each before baking.
5. 5. Bake for 18-20 minutes or until a toothpick inserted comes out clean. Allow cupcakes to cool completely.

For the Peanut Butter Filling:

1. 1. In a medium bowl, mix creamy peanut butter with softened butter and powdered sugar until fluffy.
2. 2. Scoop out a little from the center of each cooled cupcake and fill with this mixture.

For the Frosting:

1. 1. Beat together powdered sugar, creamy peanut butter, and softened butter until smooth and fluffy.
2. 2. Frost each filled cupcake generously.