Thinly slice the mushrooms and fry in a saucepan with the chopped garlic and oil.
Add the salt, pepper and chopped parsley as the mushrooms begin to cook. Put the sauce to one side for now.
Prepare the stock by boiling the vegetables, bay leaf and peppercorns in 1 litre of water for approximately 10 minutes.
In a saucepan sauté the diced onion in butter, then add the rice and fry lightly.
Add a ladle of sieved stock and continue cooking for around 15 minutes, adding stock every time it is absorbed.
As the rice begins to cook add the mushroom sauce and saffron, mix well and serve while still hot.