Spray a large non-stick pot and place over medium-high heat. Add onion, garlic, carrot and celery, season with salt and pepper and cook for 5 minutes, stirring occasionally, or until onion is translucent.
Add beef, breaking apart with a wooden spoon. Cook for 5 minutes or until beef is browned all over.
Add tomato paste and stir for 1 minute.
Add lentils, crushed tomatoes, stock and herbs. Reduce heat to low and simmer slowly for 30 - 35 minutes until the sauce is slightly thickened and reduced. Adjust seasoning.
Meanwhile, preheat oven to 355°F/fan-forced 325°F and bring a large saucepan of salted water to the boil.
6
Add pasta to boiling water and cook for 2 minutes less than packet instructions specify. Reserve ½ cup of pasta water and drain pasta, tossing with bolognese sauce. Add reserved pasta water if needed.
7
Stir through parmesan and transfer pasta to a small-medium baking dish.
8
Top with mozzarella and bake for 15-20 minutes or until cheese is melted and golden.
9
Rest for a few minutes before serving.