Begin by thawing your blackberries if they are frozen, then puree them in a blender until smooth. Set the puree aside to cool.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-5 minutes.

Once fluffy, add the cooled blackberry puree and vanilla extract. Stir until well combined. In a separate bowl, whisk together all-purpose flour, baking soda, and salt. Fold this dry mixture into the wet ingredients carefully.

Fold in the chocolate chips, reserving a quarter to sprinkle on top before baking.

Cover the dough with plastic wrap and refrigerate for at least 30 minutes.

Preheat oven to 350°F (180°C) and line baking sheets with parchment paper. Scoop and roll dough into balls, place on sheets, and bake for 8-10 minutes.

Allow cookies to cool for about 5 minutes on sheets before transferring to a wire rack to cool completely.