Coarsely chop the mushrooms and prepare the onion, carrots, and celery.
Heat olive oil in a skillet, sauté onion, carrots, and celery for five minutes. Add garlic, rosemary, and bay leaves, then stir in the tomato paste and sauté for three more minutes.
Add chopped mushrooms, season with salt and pepper, and cook on medium-high heat for about twenty minutes. Stir in balsamic vinegar before turning off the heat.
Cook pasta according to package instructions. Toss drained pasta with ragu and reserved pasta water. Serve hot topped with fresh basil and olive oil.