Wash the meat, dab dry and season with salt and pepper. Peel and finely chop the onion. Heat 1 tablespoon of oil in a small pan, fry the onion until transparent, remove from the heat and add the herbs.
Clean and sanitize the mushrooms. Heat 1 tablespoon of oil in a frying pan, fry the meat well all around, add the mushrooms and fry briefly. Spread the onion and herb mixture over the roast.
Roast in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 45 minutes. In the meantime, peel the potatoes, wash them thoroughly and cook in boiling salted water for approx. 20 minutes.
Meanwhile wash parsley, shake dry and chop finely. Take the roaster out of the oven, lift out the meat and let it rest for 3-4 minutes. Deglaze roast and mushrooms with crème balance, bring to the boil and season with salt and pepper.
Drain the potatoes. Cut the meat open. Arrange meat and mushroom sauce on a plate. Garnish with parsley. Add potatoes sprinkled with parsley.