Spread the frozen Rösti on a baking tray. Bake in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 20 minutes. Turn Rösti over after 12 minutes. In the meantime, wash the chicken fillet, dab dry and cut into cubes. Clean, clean and halve the mushrooms.
Wash and clean the zucchini and tomatoes. Cut zucchini into strips, quarter tomatoes. Wash herbs, dab off leaves. Heat oil. Fry chicken and mushrooms in it at high heat for about 5 minutes. Season with salt and pepper. Add zucchini and tomatoes, fry briefly. Deglaze with stock and white wine. Add herbs, bring to the boil.
Season with salt and pepper. Add zucchini and tomatoes, fry briefly. Deglaze with stock and white wine. Add herbs, bring to the boil. Flavour again and arrange in portions with the roasting wedges. Serve with 1 blob of crème fraîche