Place deep-frozen Rösti corners on an ungreased baking tray and bake in a preheated oven (electric range: 225°C/ gas: level 4) for approx. 20 minutes until golden brown. In the meantime, wash the meat, pat dry and cut into strips.
Clean the mushrooms and, depending on their size, leave them whole or cut in half. Peel and chop the onion. Heat oil in a pan and fry the meat in portions, remove. Fry the mushrooms and onions in the hot frying fat.
Add meat and frozen peas to the mushrooms and deglaze with broth and cream. Season with salt and pepper and stew covered for about 5 minutes. Stir the processed cheese in small pieces into the hot sauce.
Add the sauce thickener while stirring and bring to the boil again briefly. Season to taste with salt and pepper. Wash parsley, dab dry and chop except for a little bit for garnishing. Arrange the shredded meat and Rösties on plates.
Sprinkle with parsley and garnish as desired with parsley and a tomato floret.