Heat the oil in a frying pan and fry the onions for 5 minutes until beginning to soften. Stir in the garlic and cook for another minute.
Stir in the chopped tomatoes, 300ml (½pt) water and herbs and bring to the boil. Add the lentils. Reduce the heat and simmer gently for about 30 minutes until lentils are soft but still hold their shape. Season to taste
Preheat the oven to 180℃ (160℃ fan)/350°F/gas mark 4.
Place a layer of potatoes in the bottom of a deep ovenproof dish. Spoon about one quarter of the lentil mixture on top.
Repeat the layers until all the lentil mixture has been used and finish with a layer of potato. Carefully pour the stock over the potatoes.
Sprinkle the cheese over the top.
Bake in the centre of the oven for 50 minutes to 1 hour. Cover with foil if the top begins to brown too much.
Nutrition information is calculated usingan online nutrition database - is approximate and is meant as a guideline only. (It does not include seasoning with salt and pepper.)