Preheat the oven to 350°F. Line a muffin pan with 12 paper liners.
Stir together the cocoa powder, flour, baking soda, and baking powder together in a medium bowl until thoroughly combined.
In a second bowl, whisk the eggs, granulated sugar, brown sugar, oil, and vanilla together until smooth. Whisk in the buttermilk until completely incorporated. Add the dry ingredients to the wet ingredients and stir until just combined.
Pour the batter into the liners until each cup is halfway full.
Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean. Remove from pan and cool on a wire rack.
Cut a hole into the top of each cupcake with a cupcake corer, small cookie cutter or the back of a piping tip. Reserve the cupcake cores. Spoon 2 teaspoons of Chocmeister® milk chocolately hazelnut spread into each hole. Place the cupcake cores back into the holes - you may need to trim a bit off the bottom so that they fit.
For the frosting:
Beat butter at medium speed with a stand mixer or hand mixer for 2-3 minutes until smooth and creamy. Add the powdered sugar and continue to beat on medium speed until combined. Add the Chocmeister® milk chocolately hazelnut spread and beat for 30 more seconds. Add the milk and vanilla and beat until combined. If you need to thin the frosting you can add more milk, 1 teaspoon at a time, until desired consistency is reached.
Pipe the frosting onto the cupcakes with a piping tip and bag. I used an open star tip. Decorate the cupcakes with fresh berries and mint sprigs as desired.
Cupcake base adapted from www.sallysbakingaddiction.com