To make the dough, add milk to a medium saucepan and cook until bubbles form around the edge. Remove from the heat and cool down to 100 degrees. 

Sprinkle yeast over and mix to dissolve. Let sit for 5 minutes. 

Meanwhile, cream the butter, sugar, and cardamom in the bowl on an electric mixer fitted with the paddle attachment.

Pour in the yeast mixture, flour, and salt and mix until blended.

Switch to the dough hook and knead on low speed until smooth, about 5 minutes. 

Cover the bowl with plastic wrap and let proof in a warm place for 1 hour. When the dough has proofed, turn it out onto a floured surface and cut into two pieces.

While the dough is rising, make the filling. Mix the butter, sugar, cardamom, salt, vanilla bean paste until smooth. Set aside. 

Roll each piece into a rectangle and spread with the filling. Fold into thirds, fold the top over the middle of the filling and the bottom onto the middle. Slice into strips approximately one inch. Stretch the piece out and tie into a knot. 

Place on a baking sheet lined with parchment paper. Cover with a towel and let rise for 30 minutes. Preheat oven to 425°. 

When ready to bake, whisk egg and water and brush over the buns. Sprinkle half of the tops generously with pearl sugar and the other half with cardamom sugar.

Bake for 12 to 15 minutes or until buns are golden brown.