Method

1. First, make the tomato sauce. Heat the olive oil in a large saucepan over a gentle heat and fry the onion for 10-15 mins or until tender.

2. Add the tomatoes, tomato purée, oregano and vegetable bouillon, and simmer over a low-moderate heat for 20-30 mins, stirring from time to time, until thickened.

3. Meanwhile, prepare the filling. In a frying pan, heat the olive oil and fry the spring onions, leeks and garlic for 10 mins, stirring from time to time to stop them catching, until softened, then stir in the spinach to wilt.

4. For the cheese sauce, tip the ricotta and egg into a food processor and whip until smooth and light – it should not take more than a minute. Season well and stir in the 50g grated cheese.

5. Heat the oven to 200C/180C fan/gas 6. To assemble the lasagne, put some cold water in a large, flat dish. Then, one sheet at a time, soak the matzo in the water – no more than 30 seconds, as you don’t want them falling apart, just moistened and more pliable. Use the first three sheets to line the base of an ovenproof dish measuring approximately 20cm x 30cm.

6. Top the matzo with a third of the tomato sauce. Spread it over evenly, then top with a third of the ricotta mixture. Top with half the spinach and leek mixture, then a second layer of water-dipped matzo sheets. Repeat the process, then top with the last of the tomato sauce and, finally, the last of the ricotta sauce. Sprinkle with the remaining grated cheese, then cover loosely with foil – try to ‘tent’ the foil upwards so it’s not laying on the surface of the lasagne.

7. Bake for 30 mins, then uncover and bake for a further 25-30 mins to get the top nicely golden. Give it a few minutes to settle once out of the oven, and serve with a crisp green salad.