Finely chop the onions and sauté in the butter until translucent. Add the rice and sauté until it becomes translucent. Deglaze with the white wine and gradually add the broth until it is soaked up by the rice.
Cut the mushrooms into slices, finely chop the garlic and parsley and fry everything in the oil. Mix the peas, drained well, with the mushrooms.
Fold the parmesan and the mushrooms with the peas under the risotto. Season with salt and pepper and serve.