Make sure that all the ingredients are at room temperature. Dissolve the salt, sugar, cardamom and fresh yeast into the warmed up milk. Set aside approx. 200 ml flour. It should be added at the very end. Knead the dough for a while to improve elasticity. Finally, add the soft butter or margarine and continue kneading until the dough is smooth. Add the rest of the flour, if necessary. When making small buns, the dough can be softer than when making a twist. Place the dough into a bowl, tightly covered with plastic and allow to rise until doubled.
Divide the risen dough into two pieces. Roll out the dough into a flat rectangle, about 30×60 cm. Spread about half of the butter on the dough and sprinkle with half the sugar, and cinnamon according to your taste. Roll up the dough into a cylinder, leaving the seam against the work surface. Cut diagonal slices, sized 3 cm on the wider side and 1.5 cm on the narrower side. Lift the pieces onto the work surface, narrower side upwards. Press the middle all the way down to the work surface with your thumb. Place the cinnamon bun on a baking sheet and let it rise under a tea towel. Make more cinnamon buns from the remaining dough in the same way.
Brush the buns with egg and sprinkle with decorating sugar. Bake at 225°C/440F for about 10-15 minutes.