Peel and wash the potatoes and rutabaga and cut into small pieces. Cover and cook in boiling broth for about 20 minutes. In the meantime peel onions, cut into rings. Clean and wash spring onions, cut into small pieces, cut sausage into thin slices. Wash and chop parsley. Drain vegetable stock. Pour milk and cream to the vegetables and crush with a masher.
Stir in parsley. Season with salt and pepper and fill into an ovenproof dish. Spread the onion and sausage mixture on top. Sprinkle with breadcrumbs. Put butter in small flakes on top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 15 minutes and serve