Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large mixing bowl, cream the softened butter and granulated sugar together using an electric mixer or whisk until light and fluffy.
Mix in the vanilla extract.
In another bowl, whisk together the all-purpose flour, cocoa powder, salt, and baking powder. Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Use a cookie scoop or spoon to drop tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
With your thumb or the back of a spoon, create an indentation in the center of each cookie.
Bake in the preheated oven for 12-15 minutes, or until the edges are firm but the center is still soft.
While the cookies are baking, melt the chocolate chips in a microwave-safe bowl in 30-second intervals, stirring between each interval until smooth. Allow the melted chocolate to cool slightly.
Once the cookies are out of the oven and cooled for a few minutes, fill each thumbprint with the melted chocolate or your choice of jam.
Allow the cookies to cool completely before serving. Optionally, dust with powdered sugar for extra sweetness.