1. Preheat the oven to 180°C (350°F). Line a muffin tray with 12 paper liners and set aside. Mix the flour with the cocoa powder, baking powder, baking soda, and salt. Set aside.

2. Add the butter and both sugars to a large bowl and mix until light and fluffy. Add the egg and mix until well combined. Combine sour cream, milk, and vanilla extract. Add this mixture in two batches, alternating with the flour mixture, to the bowl and mix until just combined. Crumble the Oreo cookies and fold them into the batter. Transfer the batter to the prepared paper liners, filling each one about 3/4 full. Bake the cupcakes for about 20-22 minutes, or until a toothpick inserted into the center of the cupcakes comes out clean. Take them out of the oven and let them cool down completely on a wire rack.

3. Add the room-temperature butter for the frosting to a large bowl and mix on high until light and fluffy. Add the room-temperature mascarpone and vanilla extract and mix until well combined. Combine confectioners‘ sugar and cocoa powder and gradually add it to the bowl – mix until well combined. If the frosting seems too thick/firm, you can add a little heavy cream to soften it. Add the (very) finely crumbled Oreos and fold in.

4. Fill the cream into a piping bag with a large star tip and decorate each cupcake with a good amount of the cream. Press an Oreo into the cream of each cupcake and sprinkle them with some cookie crumbs to your liking (optional).