In a stand mixer bowl, add milk, butter, flour, sugar, salt, cardamom, and yeast. Mix on low speed for 5 minutes, then medium/medium-fast speed for about 30-40 minutes until the dough is formed.
Test if the dough is ready by taking a piece and stretching it to a thin windowpane.
Turn the dough out of the bowl and shape into a rectangle. Wrap the dough in plastic or place on a parchment-lined tray in the fridge for an hour.
In a separate bowl, mix soft butter, sugar, salt, and vanilla sugar or extract.
Take the dough out of the fridge, flour it, and roll it into a large rectangle. Spread the filling onto the dough and fold into thirds.
Roll out the dough and portion it into 80-90g pieces. Twist each piece into a pretzel shape and place on a baking tray.
Cover and let rise until double in size.
Preheat the oven to 200C (400F) and bake for about 8 minutes or until golden brown. Rotate the tray at the 5 or 6 minute mark to avoid overbrowning.
Let the Sockerkringlor cool completely, then brush with melted butter and dip in sugar.
Enjoy!