Remove the stalk from the eggplant, then slice it lengthways into 1cm thick slices. Place a few slices in a colander which you have set over a large bowl. Scatter salt liberally over the slices, then keep on layering the slices using up the salt as you go. Allow the eggplant to release its juice over the next hour or so.
While the eggplant is doing it’s thing, start on your sauce. Heat 2 tablespoons of oil in a large heavy-based saucepan over medium heat and then sauté the onion and garlic for two minutes. when the onion starts to soften, add the celery and carrot, stir well to thoroughly coat in oil, and sauté for a further five minutes.
Add the wine if you are using it (or half a cup of water if you are not) and allow the wine to bubble, stirring through the vegetables. When the wine has reduced by half, add the tomatoes, tomato paste, lentils, parsley and enough water to cover the contents by a further 2cm. Season with salt and pepper, add the sugar and stir well, then bring to the boil. Reduce the heat to a slow simmer, cover the saucepan and simmer gently for an hour. From time to time, give the sauce a good stir – you may have to add another cup of water if it get’s too dry. The lentils should become the consistency of cooked peas.
Heat 3 tablespoons of oil in a large heavy-based frypan and add the rinsed and dried eggplant slices, a few at a time. Fry for about two minutes on each side until they start to turn golden brown and soften – drain on paper towel.
To assemble: Preheat oven to 180°C Place a couple of large spoonfuls of lentils and sauce on the base of a large lasagne or gratin dish and smooth it out evenly. Place slices of eggplant over the top of the lentil mixture. Top with a layer of lasagne sheets. Continue layering and finish off with a layer of lasagne sheets.
Top with warm béchamel sauce, then scatter grated parmesan over the top, or mozzarella, or tasty cheese if you prefer. Bake for 40 minutes until the lasagne sheets are cooked through and the top is golden and bubbling. If you need to, cover with a layer of foil to prevent the top colouring too much while the pasta cooks through.
At this stage, you can allow it to cool to room temperature, then store it in the fridge, covered, for up three days. You can freeze it for up to one month. (Allow it to thaw before re-heating, covered in foil, for 45-50 minutes at 160°C).
Remove from oven and let it sit on the bench top for ten minutes before slicing and serving.