Preheat your oven to 180°c/360°f (fan oven).
If your are making the homemade vegan cheese for the topping go ahead an prep now, following this recipe. You can just use store bought cheese if your time poor.
Now prep the white sauce. Melt the 50g of margarine/vegan butter in a small saucepan. Once melted add in the 50g of flour and whisk together. Cook the combined flour mixture for about 30 seconds. Now slowly pour in the 400ml of plant milk whisking into the flour as you pour.
Once all of the milk has been tipped into the pan add the 50g of nutritional yeast and 2 teaspoons of dijon mustard. Whisk to combine into the sauce and bring the mixture to a simmer. Cook for about 2-3 minutes until the sauce has nicely thickened. Remove from the heat and season to taste.
Now we can make the aubergine filling. Heat the 4 tablespoons of olive oil in a large saucepan over a medium heat. Toss in the 5 cubed aubergines, 1 head of diced garlic and 4 tablespoons of soy sauce. Fry for about 5 minutes, stirring often, until the aubergine begins to soften.
Pour in the 1 tsp of dried oregano, 1 tablespoon of smoked paprika and 3 tablespoons of tomato paste and stir well to combine with the aubergine. Cook the aubergines for a further 5 minutes until they are very soft ad completely coated in the tomato sauce.
Remove the pan from the heat and stir in the plum tomatoes. Crush any large pieces of plum tomatoes so that the sauce has an even consistency. Season to taste with salt and black pepper.
Pour enough aubergine tomato sauce into a 12inchx8inch oven dish to cover the bottom. Top the tomato sauce with a generous ladle of the white sauce. Next arrange a layer of lasagne sheets to cover the white sauce. Now spoon on another layer of tomato sauce and repeat layering process until you have a further two layers of pasta.
On the top layer of pasta spoon over the final serving of aubergine, then the white sauce and finally top with an even coating of vegan cheese. If you are using the homemade cashew cheese spoon a thick layer over the white sauce and gently smooth to ensure even coverage.
Place the prepared lasagne into the preheated over and bake for 40 minutes until the pasta is soft and the cheese topping the lasagne has melted evenly and taken some colour.