Mix the sugar, butter, flour, milk, salt, sourdough starter, cardamom together in a bowl until the dough looks completely smooth cover it and let it rest.
After the dough has rested for 1 hour, do at least 4 coil folds. Cover the dough and let it rest for one more hour before you do another set of folds.
After 4-5 hours, when your dough has almost doubled in size, it is time to roll it out with a rolling pin into a square. Roll it out on a floured surface until it is about half an inch thick.
After rolling out your dough into a square take 2-3 spoons of room temp butter and spread it out as evenly as possible. Use more if you spread your dough out a little extra. Sprinkle the additional white sugar evenly over the surface, and sprinkle the ground cardamom evenly over the surface.
You are now going to fold the dough over itself in half. After folding the dough, you can use a knife to to cut the dough into long strips that are about 1 inch thick. Twist the strips around themselves, take the long end and pull it into the middle and out the bottom. Feel free to get creative and make your own shapes. After baking you might be surprised at the form it takes.
Leave the buns to rise for an additional hour or until visibly puffed up.