Brown mince in olive oil in a large pot. Transfer to another dish and sauté onions in olive oil until golden brown. Add celery, carrots, courgettes, spinach and lightly sauté with onions for another 2-3 minutes. Add tomatoes, tomato paste, soy sauce, garlic and transfer mince back into pot. Turn down heat and let simmer for 15-20 minutes, reducing the fluid by leaving the pot open.
In a separate pot, prepare white sauce with olive oil, flour, milk and seasoning.
Let lasagne sheets stand for about 10 minutes in a shallow dish with boiling water with a dash of olive oil to soften them - that speeds up cooking time.
In an oven proof dish, pack one layer lasagne to cover bottom of dish. Add half of the meat sauce, add another layer of lasagne sheets, cover with meat sauce again. Crumble over the ricotta cheese, sprinkle over half of the chopped parsley and cover with the white sauce.
Bake in the pre-heated oven for 30-45 minutes.
To serve, sprinkle with grated parmesan cheese and sprinkling of fresh parsley.