Put the stock in a saucepan and bring to a gentle simmer. Leave over a low heat.
Gently clean the ceps and other mushrooms, using a sharp knife and a brush (avoid washing them whenever possible).
If you are using dried porcini, put them to soak in a small bowl of water for 15 minutes. Slice the fresh mushrooms, putting a few good slices aside for decoration.
Fry the onion in the oil and half of the butter. When the onion begins to colour, add the sliced mushrooms and continue to fry over a moderate flame for a couple of minutes. If using dried porcini, chop them into small pieces and add to the mushrooms, keeping the water they soaked in to add to the risotto later with the stock.
Add the rice and stir for a minute, until all the grains are coated in the fat. Start to add the hot stock, ladle by ladle. Wait until each ladleful is absorbed before adding the next. Add the porcini soaking water if you have it. When the rice is al dente, remove from the heat, season and stir in the remaining butter and the Parmesan cheese. Serve hot, decorating each portion with a slice or two of raw mushroom.
First published in Two Greedy Italians Eat Italy by Antonio Carluccio and Gennaro Contaldo, published by Quadrille (£20, hardback). Photograph: ©DAVID LOFTUS
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