Heat oven to 220C/200C fan/gas 7. Brush both sides of the aubergine slices with 2 tbsp of the oil, lay on baking sheets, season and bake for 15-20 mins until tender, turning once. Cook the lentils following pack instructions.
Heat the remaining oil in a large frying pan. Tip in the onions and garlic and cook until soft. Stir though the squash and the tomatoes, plus ½ can of water. Simmer for 10-15 mins until the sauce has thickened. Stir in the lentils, basil and seasoning.
Spoon a layer of lentils into a small baking dish. Top with aubergine slices and repeat, finishing with a layer of aubergine. Scatter with mozzarella and bake for a further 15 mins until the cheese is golden and bubbling.