As is my wont, I've adapted the ingredients a little - reduced the fat, eliminated measuring chopped ingredients etc. If you'd like to make this vegetarian, just omit the pancetta and use vegetable stock.
2 tbsp olive oil
1 small onion, finely chopped
50g pancetta, finely chopped
1 small carrot, finely chopped
1 stalk celery, finely chopped
240ml canned plum tomatoes, mashed
230g green or Puy lentils
1 litre low-sodium chicken stock
salt and pepper
3 tbsp grated Parmesan cheese
The original recipe and cooking instructions can be found here.
I served it with Marcy Goldman's Garlic-Slathered Stretch Bread (adapted) from her book A Passion for Baking, cut into fingers - perfect for dunking.