Remove any damaged parts and large gills from the mushrooms. Scrape the caps and stalks and cut off the stalk ends. Wash the mushrooms several times in lukewarm water, drain and thinly slice them.

Bring the stock to the boil in a large saucepan. Add the mushrooms, cover the pan and simmer over a low heat for 10 minutes. Wash the rice well in cold water and drain. Dice the onion.

Heat the oil in a second large saucepan, add and fry the onion until golden. Fry the rice with the onions for 5 minutes, stirring continuously, then add the water and a generous pinch of salt, cover the pan and cook the rice for 20-25 minutes over a low heat.

Drain the rice and mix it with the mushrooms and their cooking liquid. Serve sprinkled with the grated Gruyere.

Serve with: fresh lettuce salad and tomato wedges, or sauteed lightly seasoned courgette slices.