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

In a mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.

In another bowl, cream the butter with the granulated and brown sugars until light and fluffy, about 3-4 minutes. Add in the vanilla extract and mix well.

Beat in the egg until fully incorporated into the butter mixture.

Gradually add the dry ingredients to the wet mixture, stirring until combined and a dough forms.

Scoop tablespoon-sized portions of dough and roll them into balls. Place them on the prepared baking sheet, ensuring adequate spacing.

Using your thumb (or the back of a spoon), make an indentation in the center of each cookie.

Fill each indentation with your chosen jam or chocolate chips.

Bake in the preheated oven for 10-12 minutes. Remove and let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.