Salt and pepper fillet pieces, fry in hot oil on all sides, lay out and leave to cool For the sour cream dough, quickly knead all ingredients into a dough, wrap in foil and leave to rest for approx. Let rest in the refrigerator for 30 minutes Roll out dough on a floured work surface as thinly as possible into a rectangle and cut in half, wrap pork tenderloin with dough, roll up, place on a prepared baking sheet, brush with beaten egg and prick several times with a fork, sprinkle with seeds or grains if desired. Bake in the preheated oven at approx. 170 °C for approx. 15 minutes, depending on the thickness. Remove from the oven, cut into slices and arrange in a pleasing way, serve with red wine sauce, herb sauce or any other sauce.