First make the gluten-free bechamel sauce, adding a little extra milk to ensure it is not too thick for good coverage. Follow the recipes for spicy eggplant, creamed spinach, and leek and yellow bell pepper layers. Set aside until required. Preheat the oven to 350°F.
Spicy Eggplant Layer: Cut the eggplant into ¾in thick slices. Heat 6 fl oz of the oil in a deep 10-12 inch skillet. When hot and almost smoking, add a few eggplant slices and cook until golden and tender on both sides. Remove and drain on a wire rack over a baking sheet. Repeat with the remaining eggplant, adding more oil if necessary.
Put the ginger, garlic, and water into a blender or food processor. Blend until fairly smooth.
Heat the remaining oil in the skillet. When hot, add the fennel and cumin seeds (be careful not to let them burn). Stir for just a few seconds, then add the chopped tomatoes, the ginger and garlic mixture, sugar, coriander, turmeric, cayenne, and salt. Simmer, stirring occasionally, until the spice mixture thickens slightly, about 5-6 minutes.
Return the fried eggplant slices to the pan and add the raisins. Mix gently with the spicy sauce. Cover the pan, reduce the heat to very low and cook for a further 5-8 minutes.
Creamed Spinach Layer: Wash the spinach and shake off the excess water. Put into a heavy-bottomed saucepan over a low heat, season and cover tightly. After a few minutes, stir and replace the lid. After about 5-8 minutes, strain off the copious amount of liquid that spinach releases and press between 2 plates until almost dry. Return to the pan, increase the heat and add the butter and cream. Bring to a boil, stir well and thicken with a little gluten-free roux if desired, or stir over the heat until the spinach has absorbed most of the cream. Season with salt, pepper, and freshly shredded nutmeg to taste.
Leek and Yellow Bell Pepper Layer: Wash the leeks and slice into ¼ inch rounds. Quarter and core the peppers and cut into ¼ inch thick slices at an angle. Heat the butter and oil in a heavy-bottomed pan, toss in the leeks and add a little water. Season with salt and freshly ground black pepper. Cover and cook on a gentle heat for about 8 minutes or until tender. Add the bell peppers, toss and add a drop more water if necessary, then continue to cook until the peppers are soft. Taste and adjust the seasoning if necessary.
Bring 8 pints water to a rolling boil in a large saucepan and add 1-2 tablespoons salt. Cook 3 or 4 sheets of pasta at a time, stir to keep them separate and cook for just 30 seconds after the water comes back to a boil. Remove, put into a bowl of cold water, then drain on a clean, dry dish towel.
Taste each component to ensure it is delicious and well seasoned. Spread a little bechamel sauce on the base of the dish, cover with a layer of barely overlapping pasta sheets and half the spicy eggplant mix. Spread the creamed spinach over the spicy eggplant and add another layer of pasta. Spread with the other half of the spiced eggplant and then more pasta. Add the leeks and yellow bell peppers next, then more pasta, ending with a layer of bechamel sauce and a good sprinkling of Parmesan cheese. Ensure all the pasta is under the sauce.
Dot with a few little knobs of butter and wipe the edges of the dish clean. (The dish may be prepared ahead to this point and refrigerated for a few days or frozen for up to 3 months.)
Bake in the oven for 35 minutes or until the lasagne is golden and bubbly on top. Allow the lasagne to rest for about 10 minutes so that the layers compact slightly. Serve from the dish.