1. Mix flour, confectioners’ sugar, and cornstarch in a bowl. Add the butter and cut into pea-sized pieces with a pastry blender*. Add the egg and vanilla extract, mix well and knead until you get a nice and smooth dough. Shape into a log, wrap it in plastic wrap, and place it in the fridge for about 1 hour (overnight is also ok).

2. Preheat the oven to 350°F (180°C). Line a baking sheet with baking parchment and set aside. Take the dough out of the fridge and cut it into 15 slices. Roll each dough slice into a ball and place them on the prepared baking sheet. Use a finger/thumb to make two indentions in the center of each dough ball. They should be connected at the bottom and resemble a heart. A small spoon helps here a lot to create the pointy tip of the heart. Fill the hearts with a little bit of jam and bake the cookies for about 10-12 minutes. Take out of the oven and let cool down on a wire rack. Store up to 7 days in an airtight container at room temperature

Tip: You might want to add less jam to the hearts because the jam tends to spill easily during baking. If you think it is not enough jam you can add that right after baking and fill the hearts up ;)