Recipe for Blueberry Jam Cookies

Whisk the egg with the powdered sugar and vanilla extract. Add the butter and mix. Pour in the flour and baking powder, and mix everything together to form a dough ball. Wrap the dough and place it in the refrigerator for 15 minutes. Take a piece of dough and roll it out not too thinly. Place some blueberry jam and fold the dough to cover the jam. Cut out with a round cutter or a glass to create a nice round cookie. Place the cookie on a baking sheet lined with parchment paper. Continue until all the dough is used up. Brush the cookies with egg yolk and bake for 15 minutes at 180°C.