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

In a large mixing bowl, whisk together the all-purpose flour, unsweetened cocoa powder, granulated sugar, baking powder, baking soda, and salt.

In a separate bowl, cream the softened unsalted butter with sugar using an electric mixer at medium speed until light and fluffy.

Add large eggs to the butter mixture one at a time, mixing well after each addition, then stir in the vanilla extract.

Gradually add the dry mixture to the wet, alternating with the buttermilk, mixing on low speed until just combined.

Fold in the fresh blackberries and dark chocolate chips gently.

Fill each cupcake liner about two-thirds full with batter and bake for 18-20 minutes.

Once baked, allow to cool for 5 minutes in the pan before transferring to a wire rack.