Heat the oil over medium heat and add the onions and carrots. Cook until translucent, about 3 minutes. Add the mushrooms and garlic. Cook until the mushrooms have started to soften, another 3 minutes. Once the veggies have softened, add the lentils and sauce. Cook until the sauce begins to bubble, then reduce heat to low.

Stir in the milk (if using, for thinner sauce) and the dried herbs, salt, and pepper to taste. Simmer for 10-15 minutes.

While the sauce is simmering, cook the pasta according to the package instructions. Drain and return it to the pot. Add 1-1½ cups of sauce to the pasta. Stir to coat the noodles.

Serve noodles topped with additional sauce. Sprinkle with chili flakes if desired.