Rinse the lentils under plenty of cold water, checking for any impurities.
Heat the olive oil in a pan, then sweat the onion, celery, carrot, pumpkin and garlic on a medium heat for a couple of minutes.
Stir in the lentils, mushrooms and bay leaves and cook for a couple of minutes.
Add the passata and stock, bring to the boil, then lower the heat and gently simmer for about 1 hour, until the lentils are cooked.
You may need more or less stock depending on the type of lentils, so add this gradually.
Near the end of the cooking time, bring a large pot of salted water to the boil and cook the pasta until ‘al dente’.
Using tongs, transfer the pasta to the lentil ragu, mixing well and adding a little of the hot pasta water to loosen the sauce.
Remove from the heat and serve with rustic bread, a drizzle of olive oil and some chilli flakes, if desired.
