Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

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

In another bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Gently fold in the halved blackberries.

Drop spoonfuls of the cookie dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes or until the edges are golden brown.

Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.