Slice the mushrooms and onion after washing them.
Add olive oil to a pan and sauté the onion and mushrooms.
Once cooked, set them aside.
Add olive oil to the pan again and sauté the rice.
Mix in the sautéed mushrooms and onion.
Pour in a little water at a time, cooking the rice gradually.
Season with salt and pepper.
Add basil pesto and mix just before finishing.
Top with Parmesan cheese to taste.