Mix the flour, salt and sugar in a bowl. Crumble the yeast, add. Pour in the milk, mix. Knead the dough for approx. 5 mins. using the dough hook on a hand mixer. Add the butter, knead for approx. 5 mins to form a soft, smooth dough. Cover the dough and leave to rise at room temperature for approx. 2 hrs.
Divide the dough into 16 portions, shape into rolls. Use the handle of a wooden spoon to press down in the middle of the buns and create the characteristic bulges. Place the rolls on two baking trays lined with baking paper, cover and leave to rise at room temperature for approx. 30 mins.
Beat the egg, brush the rolls twice with the egg.
Bake each tray for approx. 15 mins. in the centre of an oven preheated to 220°C. Remove the rolls from the oven, leave to cool on a cooling rack.