Step 1

Preheat the oven to 200C/180C Fan/Gas

Step 2

Heat the olive oil in a large, non-stick saucepan and fry the onion for 3–4 minutes, or until softened and lightly browned, stirring. Add the aubergine, courgette, pepper and mushrooms and fry for 12 minutes, stirring regularly.

Step 3

Add the garlic and cook for a few seconds more, then stir in the red lentils, tomatoes, Italian seasoning, sugar and crumbled stock cube.

Step 4

Refill one of the tomato tins with water (400ml/14fl oz) and pour into the pan. Stir well, bring to a simmer and cook for 15 minutes, stirring regularly. Add the spinach leaves, a handful at a time and cook for 1–2 minutes more.

Step 5

While the vegetables are simmering, make the white sauce. Heat the oil in a medium saucepan. When it is hot add the flour and cook, stirring all the time, for 1 minute. Stir in the milk, yeast, bay leaf and nutmeg and season well with salt and pepper.

Step 6

Bring to a simmer, whisking constantly with a metal whisk over a moderate heat for 4–5 minutes, or until smooth and thickened. (Use a silicone covered whisk if using a non-stick saucepan.) Adjust the seasoning to taste – you’ll need more black pepper than you might imagine.

Step 7

Spread a third of the vegetable mixture over the base of a 2½ –3 litre/4½– 5 pints ovenproof lasagne dish and cover with a single layer of lasagne sheets. Top with another third of the vegetable mixture (don’t worry if it doesn’t cover evenly) and a second layer of lasagne.

Step 8

Pour over just under half of the white sauce, after removing the bay leaf, and very gently top with the remaining vegetable mixture. Finish with a final layer of lasagne and the rest of the white sauce.

Step 9

Bake for 35–40 minutes, or the pasta has softened and the topping is nicely browned and bubbling. Stand for 5 minutes before cutting to allow the filling to settle.