Carefully, with a coffee spoon, remove the inside mushrooms. Chop the stuffing and Reserve.
Place the mushrooms on a tray with a drizzle of olive oil, salt and pepper. Bake for about 10 minutes.
Meanwhile, in a saucepan, place a drizzle of olive oil, chopped garlic and finely chopped rosemary. Add the chopped walnuts as well as the minced mushroom stuffing.
Add the rice and let it fry for a minute. Then add hot water and season with salt. Cover and let cook over low heat for 10 minutes.
Remove the mushrooms from the oven and fill with the rice. Finish with grated parmesan cheese. Take it back to the oven for another 10 minutes.
