Prepare the Cookie Dough:

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

Add the egg and vanilla extract, mixing until fully combined.

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until the dough comes together.

Chill the Dough:

Once the dough is ready, cover the bowl with plastic wrap and refrigerate it for about 30 minutes.

Form the Cookies:

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

Roll the dough into small balls about 1-inch in diameter. Place them on the prepared baking sheet, spacing them a few inches apart.

Use your thumb or the back of a spoon to create a small indentation in the center of each dough ball.

Add the Jam Filling:

Spoon a small amount of mulberry jam into the center of each indentation. Be careful not to overfill it, as the jam can spill over while baking.

Bake:

Bake the cookies for about 10-12 minutes or until the edges are lightly golden. Let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.

Serve:

Once cooled, your cookies with mulberry jam are ready to be enjoyed!