Defrost spinach on a sieve. Clean, wash and finely chop the spring onions and radishes.
Stir the whole quark and milk until smooth. Season to taste with salt and pepper. Stir in spring onions and radishes. Rinse sprouts and drain well.
Defrosted spinach well squeeze and chop coarsely. Peel and finely chop the onion. Peel, wash and finely grate the potatoes. Mix well with egg, flour, onion and spinach. Season with salt and pepper.
Heat the oil in portions in a coated pan. Fry 16-20 golden brown Rösti from the potato mixture. Warm the finished Rösti in the oven. Serve with radish quark and sprouts.