Split the whole almonds in half and reserve for decoration.
Line a baking tray with parchment paper.
Cut the marzipan into pieces and put it into a bowl.
Add the ground almonds, confectioners' sugar, flour, egg, and almond extract and knead by hand until a smooth ball forms.
Cover in plastic wrap and let it rest in the fridge for about 30 minutes.
Preheat the oven to 350˚F (180˚C).
Once rested, shape the dough into little balls the size of a big cherry or a small walnut. You can do this by dividing the dough, then rolling it to two strands to the diameter you want and cutting those strands into appropriately sized chunks. Roll these chunks into spheres between your palms.
Decorate each ball with three almond halves, the tips of the almonds pointing into the center.
Put the decorated Bethmännchen onto the prepared baking sheet.
Once the sheet is full, glaze with egg yolk.
Bake for about 20 minutes- the tops should be golden, while they should still be very light near the bottom.
They keep in an airtight container for several weeks.