1. Cut the meat into 1-inch cubes. Peel the vegetables. Slice the carrots and celery, and cut the mushrooms and onions into quarters.
2. Place the onion and oil in the bowl fitted with the mixer. Launch the P1 simmer program at 270°F for 3 minutes.
3. Roll the meat in flour. Place the ribs, bouquet garni, carrots, celery and broth in the bowl. Season with salt and pepper. Launch the P2 simmer program at 210°F for 30 minutes. At the end of the program, add mushrooms and relaunch the P2 simmer program for 30 minutes.
4. At the end of cooking, remove 1 cup of the broth and mix with the sour cream. Place the meat and vegetables on a plate and cover with the sour cream sauce. Serve immediately.