To make the dough, crumble the yeast into a bowl and add the milk. Add the cardamom, salt and knobs of butter, then add the sugar. Add the flour in small parts and knead the dough for 5-10 minutes with your hands or in a mixer until smooth. Cover the dough and let it leaven for 30 minutes.
Meanwhile, combine all of the ingredients for the filling together in a medium bowl.
Roll the dough into a rectangle and spread the filling on top. Fold the dough lengthwise and roll lightly. Slice into strips and tie each strip into a knot.
Place the buns on a baking tray and let them leaven for 2 hours.
In a small saucepan, boil the ingredients for the syrup until the sugar is dissolved. Let it cool.
Mix the sugar and cardamom together in a small bowl.
Preheat the oven to 200C/400F. Beat the egg, water, and salt for the egg wash. Brush the buns with the mixture and bake for 12-15 minutes or until golden brown. Brush with the syrup and sprinkle with sugar and cardamom. Serve warm or at room temperature.
