In a large saucepan, sear the meat in portions with 1 tablespoon of oil over high heat on each side until it is brown and crispy and then place on a plate.
Pour the remaining 2 tablespoons of oil into the saucepan and simmer the finely chopped onions and celery pieces over medium heat for about 4 minutes. Repeatedly scrape off the brown pieces sticking to the bottom of the pot with a wooden spoon and stir in. Then stir in the flour and let it fry briefly. Then add the poultry stock while stirring constantly and bring to the boil. Add the mushrooms, paprika powder, tomato paste and meat, along with the meat juice that has formed on the plate, season with salt and pepper and let the stew simmer for about 1.5 hours.
Then add the peppers and simmer for another 30 minutes.