1. Adjust an oven rack to the middle position and heat the oven to 400 degrees. Bring the broth and bay leaves to a simmer in a medium saucepan over medium-high heat. Cover and keep the broth warm over the lowest possible heat.
2. Melt the butter in a large saucepan over medium heat. Add the onion, porcinis and ½ teaspoon salt and cook until lightly browned, about 9 minutes. Stir in the rice and cook until the edges begin to turn translucent, about 3 minutes. Stir in the garlic and saffron (if using) and cook until fragrant, about 15 seconds. Add the wine and cook, stirring frequently, until it is completely absorbed, about 2 minutes.
3. Spread the rice mixture into a 9 by 13-inch baking dish. Pour the warm broth over the top. Bake until the rice is tender and the liquid is absorbed, 25 to 30 minutes.
4. Saute cremini mushrooms over medium high heat until browned, about 10 minutes. Stir theParmesan and mushrooms into the baked risotto. Season with salt and pepper to taste.