Chop, flake and crumble the fat into the flour. Stir in the egg yolks and sour cream. Mix everything very well till smooth dough. It is very important, that you will mix the dough very well. You can use your hands.
Separate the pastry into balls of around 300 g. Put on a tray, cover with cling film and leave to rest in the fridge, preferably overnight.
Remove the skin from the walnuts or almonds by heating them in a frying pan or in the oven (app. 200 gr C), then, while they are warm, placing inside a clean tea-cloth and rubbing, but not too hard. If there are still skin, try to remove it with a knife. Please pay attention, that walnuts should be warm, else the skin will not be removed. So if you have many walnuts, fry them in small parts. Let it be chilled. Crumble the skinned nuts and mix with the sugar. Add the powdered cardamom.
Preheat the oven to 200C.
Roll out each pastry ball into a round 15-20 cm in diameter. Cut the round diagonally into eight triangular pieces. Spread a thin layer of nuts and sugar onto each triangle. Roll the triangle into a cigar shape, starting from the larger end.