Wash the meat and put it into a pressure pot, add pepper seeds, onion (cut in half and toasted), 2 litres of water (up to half volume of the pot), close the pot and heat up over high heat until the pot starts to whistle, then set to moderate heat and cook for 30 minutes. Turn off and leave to rest for 10 minutes, then step aside and press the red button (first lightly and then fully) to release all the steam. Open the pot carefully, strain the soup and turn it back into the pot which you washed in the meantime. Separate the meat from bones, chop it finely and add it to the soup. Dice the roots into the soup and season with salt, pour some more water and close the pot, put it back on the hob and set to maximum.
When it starts whistling, set to moderate heat and let cook for other 5 minutes, turn off and wait for 5 minutes, release the steam and open the pot. Add salt to taste and water as pleased.
In a small skillet fry edible oil and flour until golden and pour into the soup, let simmer for few minutes. Take off the heat, mixing slowly add sour cream with egg yolk that you previously whisked together, leave to rest 5 minutes then add finely chopped parsley.
Serve well warm with lemon juice or some more sour cream to taste.