Melt the butter in a large, heavy saucepan over medium heat. Add the onions and sauté until tender, about 8 minutes. Add the white mushrooms, porcini mushrooms, and garlic; sauté until the mushrooms are tender and the juices evaporate, about 10 minutes. Stir in the rice. Add the wine; cook, stirring often, until the liquid is absorbed, about 2 minutes. Add 1 cup of hot broth; simmer over medium-low heat, stirring often, until the liquid is absorbed, about 3 minutes. Continue to cook until the rice is just tender and the mixture is creamy, adding more broth by cupfuls and stirring often, about 28 minutes. Stir in the peas. Mix in the Parmesan cheese. Season with salt and pepper to taste.