In a large saucepan, heat oil over medium heat. Add onions, mushrooms, courgette and garlic. Cook and stir until tender, about 5 minutes.
Add lentils and 750ml water to vegetables. Bring to a rolling boil, stirring occasionally. Reduce heat to low, cover, and cook 45 to 60 minutes.
Stir in passata, tomato purée, sugar and remaining water. Bring to the boil. Reduce heat, cover, and simmer for 20 minutes. If necessary, add more water to keep the sauce from sticking. Be careful not to dilute; the sauce should be quite thick.
This was easy to make and very filling, but in my opinion it could have done with some herbs and/or spices to give it more flavour. I agree with other reviewers who suggested to add the mushroom and courgette towards the end of cooking, otherwise they'd come out a bit soggy! - 22 Jun 2012
I suggest adding the mushrooms and courgette 10 minutes before serving, so they do not become mushy and hold their shape - 24 Jul 2008
Used different ingredients.
Great hearty texture. I added Italian spices and a pinch of cinnamon. - 24 Jul 2008