First cook the brown rice in a little salted water for 10 minutes, then add the normal rice and cook for another 10 minutes. Rinse with cold water, strain well and set aside.
Set up a pan with a little oil and sauté the onion in it. Add the mushrooms (eighths or sliced), season with salt and pepper and fry for about 3 minutes. Then add the rice and mix everything well. Add the poultry stock, parmesan and parsley as well as the garlic and fry everything on a low heat for another 5 minutes.
If you like, you can add a dash of water. Season to taste with salt and pepper.