Finely chop the onion. Set aside. Clean the mushrooms and slice them. Set aside. Pluck the thyme leaves. Wash and dry them. Set aside.Measure out the ingredients and place everything near the stove so that you can work quickly. Sauté the onion in a tablespoon of olive oil, then add the measured rice. Stir continuously, and when the rice is completely heated through (touch it with the back of your hand to check), pour in the white wine. Stir and allow to evaporate completely.
Once the wine has evaporated, add a little hot stock and stir. Cook by continuously adding hot stock as it evaporates from the rice, adding it with a ladle and stirring. Cook until the rice is tender, but do not overcook it; cook it al dente. This takes about 30 minutes. At the end, stir in 30 g of cold butter.
Fry the mushrooms in a pan until red, by heating 40 g of butter, adding the mushrooms, salting and peppering them, sprinkling them with thyme and allowing them to release their juices, then letting the juices evaporate completely. Fry for a few minutes, then mix into the rice.
You can also add a little grated Parmesan cheese and finely chopped parsley on top.