Wash the potatoes and cook in plenty of boiling water for 20-30 minutes. Quench cold and remove the skin. Press potatoes hot through a potato ricer and mix with semolina.
Then stir in flour, egg, fat, cheese, 1 teaspoon salt and nutmeg. Wash parsley, dab dry and chop finely, except for a little to garnish. Add to the potato dough. Pour the mixture into a greased and semolina sprinkled Savarinform (1 litre capacity) and smooth it down.
Place the mould in the fat pan of the oven and pour hot water into the fat pan. Cook in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 1 - 1 1/4 hours. Cover in between. For the vegetables, wash the tomatoes, cut them in half, remove the seeds and cut them into slices.
Clean the mushrooms and cut into thick slices. Clean and wash spring onions and cut them into pieces. Heat the fat in a pot and fry the mushrooms thoroughly. Add tomatoes, braise briefly and deglaze with stock and cream.
Add spring onions and cook everything for a few minutes. Stir in cheese and season with salt and pepper. Turn the finished Savarin hot onto an ovenproof dish. Sprinkle with grated cheddar and bake in the oven for another 5-10 minutes (electric oven: 200 °C/ gas: level 3).
If necessary, lift to another plate, place vegetables in the middle and serve garnished with parsley.