Cut cold butter into small pieces. Mix flour, salt and baking powder, add butter and chop everything together to make crumbs.
Add sugar, egg and yolk beaten together. Mix to make a homogeneous dough.
Roll the dough into sausages with a diameter of 5–6 cm, wrap in plastic wrap and refrigerate for 30–60 minutes.
Preheat oven to 180°C. Line 2 baking sheets with baking paper. Using a hot, wet knife, cut the dough into 2 cm thick circles and arrange on baking sheets.
Use your thumb to make a well in the center of each cookie, and use a small spoon to spoon in a little jam. Bake until golden brown, about 25 minutes. Cool before serving.