Prepare the yeast dough and let it rise for about 40 minutes.
Mix cinnamon, sugar and vanilla sugar. Coarsely grate the marzipan. Whisk the egg and stir into the marzipan with a fork. Melt butter and let it cool down.
Knead the dough briefly on a little flour. Roll out to a rectangle (approx. 35 x 65 cm). Spread with 2⁄3 lukewarm butter. Spread the marzipan mixture on top, leaving an approx. 2 cm wide rim all around.
Spread marzipan lightly with a spoon. Sprinkle cinnamon-sugar mixture over it. Roll up the dough from the long side.
Place the roll of dough on a sheet of baking paper and almost cut through lengthwise. Carefully twist the strands of dough into a cord and lay them in a wreath. Press the ends together. Lift onto a baking tray with the baking paper.
Spread with the rest of the butter. Cover and leave to rise in a warm place for about 20 minutes.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Bake the wreath in a hot oven for 25-30 minutes. After approx. 20 minutes, cover with aluminium foil if necessary. Pull the wreath and paper off the baking tray and let it cool down.