1. Melt the margarine and sauté the onions.
2. Add the tomatoes, lemon juice, sweetcorn and chicken.
3. Make the cornflour-based cheese sauce with two-thirds of the cheese.
4. Layer in trays: chicken sauce, lasagne and cheese sauce, finishing with a layer of cheese sauce
5. Sprinkle with the remaining grated cheese and grated nutmeg.
6. Cook at 180C, 350F, Gas 4 for 40 minutes.