Crumble the yeast and stir it in a bowl with sugar until the yeast is liquid. Melt butter in a saucepan, add milk and remove from heat. Mix 550 g flour and 1⁄2 TL salt in a bowl.
Peel the banana. Mash the banana and 1 egg and add to the flour. Add the milk mixture and yeast as well and knead everything immediately with the dough hooks of the mixer to a smooth dough. Cover and leave to rise in a warm place for about 45 minutes until the dough volume has doubled.
Line baking tray with baking paper. Knead the dough well again. Knead in the chocolate drops, except for 1 tablespoon. Divide dough into 3 portions. Form into 3 rolls (each approx. 55 cm long) on a floured work surface.
Rollers to braid. Lay diagonally on the sheet. Leave in a warm place for another 25 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Whisk 1 egg and coat the plait with it. Sprinkle the remaining chocolate drops on top and bake in the hot oven for 25-30 minutes.
Remove and let it cool down on a cake rack.