For 4-6 servings:
Slice the aubergines, sprinkle with sea salt and leave for about half an hour for the water to drain off. Dry, and arrange in an oiled ovenproof dish, and brown both sides in the oven. Remove the dish from the oven, leave to cool, then chop the aubergines with a half-moon chopper. Tip them into a bowl and add the ricotta, the chopped walnuts, a little Parmesan, a handful of chopped sage leaves, and mix well.
Cut the pastry into sqaures, and place a small pile of the filling on each, then fold over, seal and shape into tortellini. Cook in plenty of salted water or in vegetable stock, then pour over the tomato sauce and sprinkle with Parmesan cheese.