Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
If desired, add a few drops of purple food coloring to the dough and mix until evenly distributed.
Scoop out tablespoons of dough, flatten slightly, and place a small dollop of blueberry jam in the center.
Fold the dough around the jam to seal, forming a ball, and place on the prepared baking sheet.
Sprinkle the tops with granulated sugar.
Bake for 10-12 minutes, until the edges are set but the centers are still soft.
Allow to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
Prep Time: 20 minutes | Cooking Time: 12 minutes | Total Time: 32 minutes
Kcal: 120 kcal per cookie | Servings: 24 cookies
