For the buns:

1. In a bowl attached to a stand mixer with the hook attachment, pour the yeast into the warm milk and let it dissolve for about 5 minutes. Stir to fully incorporate the yeast. 
2. Add the egg, flour, sugar, cardamom, and salt and mix until a dough forms around the hook. Add the butter and let is mix into the dough. Remove form the bowl and knead well on a well-floured surface. Put the dough in a blow and cover with a dish towel and let rise until it's doubled in size (1-2 hours).

For the filling: 

1. Combine all the ingredients except the egg in a mixing bowl attached to a stand mixer with the paddle attachment and mix until combined.  

For the assembly:

1. Split the dough in half and put on a well-floured surface. Roll out into a 12 x 16-inch rectangle, spread the filling mixture over the half of the dough lengthwise. Fold the plain dough over the filled dough, then cut lengthwise in 3/4 inch lines. 
2. Wrap each piece around two of your fingers twice to create a roll then loop the remaining length around the top twice, tucking the end underneath.
3. Set the knots on a baking sheet covered in parchment and let rest for 30 minutes. They will grow quite a bit resting and in the oven, so leave enough space between each knot. Once risen, brush the beaten egg over the buns. 
4. Bake at 350 degrees for 20-25 minutes.