To activate the yeast – stir the yeast into the lukewarm milk. (The milk should not be warmer than 40°C/104°F). Leave to rest for 10 minutes. You should see little bubbles forming at the surface.
In a large bowl combine the flour, sugar, butter, egg, salt and yeast-milk mixture. Using a hand- or stand mixer with a dough hook, mix the ingredients to a thick dough. You can also use your hands to knead the dough. Knead for at least 10 minutes. Should your dough be too sticky you can add a little more flour.
Form the dough into a ball and place it in a bowl. Cover the bowl with a tea towel. Leave to rise in a warm place for at least an hour. After this time the dough should have roughly doubled in size.
Remove the dough from the bowl and knead it again for a couple of minutes. Save about 2 tablespoon of chocolate drops to decorate the top later. Try to flatten the dough (see picture) and cover it with chocolate chips. Knead in the chocolate chips. You do not want to knead the dough for too long, as your hands will be warm. Also, kneading for too long might cause the chocolate to melt.
Shape the dough into a thick roll and then cut off about 10 parts and roll them with your hands into round bread roll shapes. I weigh my rolls individually to make sure they are of roughly equal weight. Now press the remaining chocolate drops onto the top of the buns to decorate.
Place them on a baking tray lined with parchment. Cover with a teatowel and leave to rise for a further 30 minutes.
In the meantime mix the tablespoon of milk with the egg yolk. Preheat your oven to 180°C or 356°F
After 30 minutes brush the buns with the egg-milk mixture.
Bake in the oven for about 20-25 minutes, depending on your oven. Best check them after 20 minutes. Prick with a skewer, if it comes out clean they are done.
Leave to cool before consuming.