In a small sauce-pan warm milk with sugar and cardamon to 37°C (98.6°F). You can dip your finger into the milk to check, if it's too hot let it cool down.
Place the yeast in a large mixing bowl and pour over the milk mixture and stir until the yeast has melted. Use a stand mixer with dough hook.
Cut the room temperature butter into small pieces.
Add butter, salt and half of the flour into the mixture.
Mix until combined and then add the rest of the flour.
Knead well so that the dough becomes smooth and don't stick to your fingers. About 5 min with a stand mixer or 10-12 min by hand.
Cover the bowl with plastic wrap and allow it to rise until double in bulk (for about an hour).
Now you decide what you want to do with the dough. Cinnamon bun, Semla, Sun bun or just make round buns and eat them as they are.
Cover with a towel and allow to rice again until double in size (35-40 min).
Preheat the oven to 200° C.
Beat the egg and brush the buns
Bake for 10 minutes until you reach your desired level of golden brown.