Melt the butter and add the milk.
When the mixture is finger-warm, crumble the yeast into it.
Add salt, sugar, cardamom, and flour.
Knead well, preferably in a stand mixer.
If necessary, add a little extra flour so the dough releases from the bowl.
Let rise for 30 minutes.
Roll into 14-16 buns – let rise again for 45 minutes.
Brush with 1 egg
Bake for about 10 minutes in a conventional oven at 225 degrees Celsius (437 degrees Fahrenheit).
When the bun has cooled, cut it in half and pipe a few rounds on the lower part of the bun.
A big dollop of Nutella is placed in the middle of the bun and the upper bun is placed on top as a lid.
Dust with powdered sugar.