1. 1. Preheat your oven to 350°F and line a baking sheet with parchment paper.

2. 2. In a medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and salt.

3. 3. In a large bowl, beat the softened unsalted butter, granulated sugar, and brown sugar until light and fluffy. Then, add the egg and vanilla extract, mixing until well combined.

4. 4. Gradually add the dry ingredients to the wet mixture, stirring until they are fully incorporated.

5. 5. Scoop the dough into balls and place them on the prepared baking sheet. Using your finger, make a small indentation in the center of each cookie.

6. 6. Fill each indentation with a dollop of blueberry jam. If desired, add a drop of purple food coloring to the jam for a pop of vibrant color.

7. 7. Lightly sprinkle the tops of the cookies with granulated sugar.

8. 8. Bake the cookies for 10–12 minutes, or until they are set around the edges but still soft in the center.

9. 9. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.