Heat olive oil in a large skillet over medium heat.
Add chopped onions, carrots, and celery, sauté for 5 minutes.
Add grated garlic, rosemary, bay leaves, and tomato paste. Sauté for another 3 minutes.
Add the Mushrooms
Incorporate the chopped mushrooms and season with salt and pepper.
Cook on medium-high heat for about 20 minutes, letting moisture evaporate.
Stir in balsamic vinegar and adjust seasoning if necessary.
Serving
Cook 12 ounces of pasta in salted boiling water according to package instructions.
Once al dente, reserve a cup of pasta water before draining.
Add drained pasta to the ragu pan with reserved pasta water, toss gently to combine.
Serve with fresh basil leaves and optional parmesan cheese.
Notes
Store leftovers in an airtight container in the fridge for up to 5 days. For longer storage, freeze in safe containers for up to 3 months. Thaw before reheating. For deeper flavor, use a mix of different mushrooms.