The recipe yields 15 pieces.
Put flour, sugar, and salt in a stand mixer.
Mash the boiled potatoes and mix them into the flour mixture.
Add egg yolks and lukewarm milk mixed with yeast, and add the mixture to the stand mixer.
Let the dough mix in the bowl for 3-4 minutes.
Add soft butter to the mixture and let it mix for 3-4 minutes (the dough will be quite soft).
Transfer the dough to a bowl greased with a little oil and let it rise for 2 hours with a damp cloth over it.
Shape the burger buns into approximately 15 equal pieces.
Then place them on a baking sheet covered with baking paper (make sure to give them good spacing).
Press the buns slightly flat on the baking sheet so they get the right round shape.
Let them rise for another 30 minutes.
Put the buns in a preheated oven at 180 degrees Celsius (356 degrees Fahrenheit) (fan) for 20-25 minutes.