Season chicken thighs well with salt and pepper.
Heat fat on medium high in a heavy bottomed dutch oven or casserole.
Brown chicken in fat with skin side down for 5 to 8 minutes, or until a deep golden brown. Turn and brown the other side for about 5 minutes. Remove from pot and set aside.
Pour off all but a tablespoon of fat. Cut pepper, discarding seeds and ribs. Chop onion. Add to chicken fat and fry, scraping up browned bits from the bottom of the pot.
When onions are starting to turn colour and the pepper is a vivid green, remove from heat. Let the pot cool for a minute, then add paprika. Stir paprika to thoroughly coat the vegetables and let it cook in the hot pot for a minute, but do not return it to heat. Paprika scorches very easily and it will ruin your sauce.
Stir in the chicken stock and return the pot to the burner. Reduce the heat to a bare simmer.
Nestle the chicken thighs in the sauce and cover. Let simmer for 45 mins.
After 45 mins and when the chicken is very tender, remove the thighs to finish the sauce. Meanwhile, make nokedli and then return to finishing the paprikash.
To finish the sauce: Mix sour cream and flour together until well blended. Add a small amount of cooking liquid to the sour cream mixture to avoid curdling. Slowly add more and more liquid until the mixture is doubled in volume, then begin adding it slowly to the sauce in the pot. Stir well after each addition. Keep your eye on the colour, you don't want it to become too pale. Don't feel as if you have to use all the cream mixture. If you are happy with the colour and consistency, stop. Nestle the chicken thighs back in the finished sauce and let them warm up.