2 large or 3 small aubergines, sliced into 5mm/¼in rounds
1 bunch basil, chopped
2 garlic cloves, crushed
1 tsp Dijon mustard
1 x 400g tin chopped tomatoes
500ml/18fl oz passata
50g/1¾oz plain flour
salt and freshly ground black pepper
2 tsp caster sugar
4 tbsp olive oil
50g/1¾oz butter, plus extra for greasing
568ml/1 pint milk, warmed
100g/3½oz Parmesan (or a similar vegetarian alternative), grated
6–7 sheets dried lasagne