Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.

In a medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, granulated sugar, baking powder, baking soda, and salt until well combined.

In a separate large bowl, use an electric mixer to cream the softened unsalted butter until it’s smooth and fluffy. Gradually add in the eggs, mixing well after each addition.

Slowly alternate adding the dry mixture and buttermilk to the creamed butter and eggs, beginning and ending with the dry ingredients. Stir gently until just combined, then fold in the fresh blackberries and dark chocolate chips.

Spoon the batter into the prepared cupcake liners, filling each about two-thirds full. Bake for 18–20 minutes or until a toothpick inserted comes out clean or with a few crumbs.

Once baked, remove the cupcakes from the oven and let them cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

While the cupcakes cool, prepare your frosting. Once the cupcakes are completely cooled, frost generously.