Place celery, carrots and onions in a food processor and pulse until finely chopped.

Heat 2 tbsp olive oil in a large pot over low to medium heat and sauté the onion mixture for 8 minutes or until softened.

While the onions are cooking, place the mushrooms in the food processor and finely chop. Add to the onion mixture and sauté an additional 4 minutes.

Add the salt, pepper, thyme, lentils, vegetable broth, tomato paste, balsamic vinegar and crushed tomatoes, bring to a boil, reduce to a simmer and cook covered over low heat for 45 minutes to 1 hour or until lentils are tender.

While the sauce is simmering, cook the pasta according to package directions.

Remove the bay leaves and thyme stems from the sauce. Toss the pasta with the bolognese, sprinkle with parmesan and fresh basil if desired.