Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. Beat in the egg and vanilla extract.
In a separate bowl, whisk together the cocoa powder, flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Gently fold in the fresh raspberries.
Drop by rounded tablespoons onto the prepared baking sheet.
Bake for 10-12 minutes, or until the edges are set and the centers are slightly soft.
Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
Notes
For extra fudginess, underbake the cookies slightly. Store in an airtight container at room temperature.