Start this recipe by laying the aubergine slices on 2 baking trays covered with baking paper. Season well with salt and pepper and cook in the oven for 20-25 minutes until soft and cooked through. Meanwhile, heat the remaining olive oil in a deep pan and sauté together the chopped garlic and leek for 3 minutes. Add in the diced chicken breast and brown together for another minute. Next, add in the chopped tomatos and cook for a further 2 minutes. Add the contents of the tomato soup packet, along with the cold water and mix well until the soup thickens and you obtain a lovely thick sauce. Remove off the heat, stir in the chopped basil and put aside. You are ready to put the dish together. Spread 2 tablespoonfuls of the chicken sauce onto the bottom of a large, deep ovenproof dish. Cover with 1/3 of the sliced aubergines. Carefully cover with ½ of the ricotta cheese, spreading out evenly. Spoon over ½ of the chicken sauce followed by 50g chopped walnuts and 1 tablespoon of the grated cheese. Repeat this process again, finally covering with the last of the aubergine slices. Pour over the béchamel sauce and spread out. Sprinkle over the remaining 50g of walnuts, followed by the remaining tablespoon of grated cheese. Bake in the oven at 200`c, for 25-30 minutes. Remove from the oven and allow the lasagna to set for 10 minutes before serving.