Heat the olive oil in a large pan over medium heat. Add the chopped onions and cook until they become translucent, about 3-4 minutes.
Add the minced garlic and sliced mushrooms to the pan. Cook for another 5 minutes until the mushrooms start to brown.
Stir in the Arborio rice and cook for 2 minutes, ensuring the rice is well coated with the oil and mixed with the other ingredients.
Add the diced tomatoes (without the juice) and continue to cook for 2 minutes, stirring occasionally.
Begin adding the vegetable stock, one ladle at a time, stirring continuously. Allow the liquid to be absorbed before adding more stock. Continue this process until the rice is creamy and cooked al dente, which should take about 20-25 minutes.
Season the risotto with dried oregano, dried basil, salt, and black pepper. Stir well to incorporate the seasonings.
Remove the risotto from the heat and let it rest for a minute. Taste and adjust the seasoning if necessary.
Serve the Tomato and Mushroom Risotto hot, garnished with fresh basil leaves and a generous sprinkle of grated Parmesan cheese.
