Drain the cherries. Boil up the cherry juice, cinnamon and lemon juice. Stir cornstarch in a little water until smooth and bind the juice with it. Stir in sugar and cherries and let cool down.
Separate the egg. Stir marzipan and egg white until smooth. Remove the dough from the roll, unroll and divide into triangles. Place some marzipan paste and stewed cherries on each triangle and roll up loosely from the broad side.
Place on a baking tray lined with baking paper. Mix the egg yolk with a tablespoon of water and spread the croissants with it. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 12-15 minutes until golden brown.
Take out, let it cool down a little and serve dusted with icing sugar. Makes 6 pieces.