Peel the onions, garlic, carrots and kohlrabi and finely dice. Wash and finely dice the celery.
Heat the oil in a large pan.
Add the onion and garlic and cook until softened. Add the minced meat and fry until browned and broken up with a spoon.
Gradually add the remaining diced vegetables and fry, stirring.
Pour in the red wine and add the tomatoes.
Season with salt, pepper and oregano and simmer for 30-35 minutes over a medium heat. Stir occasionally with a wooden spoon and lightly crush the tomatoes. Preheat the oven to 180°C (160°C fan, gas 4).
Meanwhile, make the bechamel sauce. Melt the butter in a pan.
Sprinkle in the flour, stir and cook until pale golden.
Pour in the milk and stir vigorously with a whisk until smooth. Cook for 1-2 minutes until thickened. Season with salt, pepper and nutmeg.
Line the base of a greased baking dish with lasagne sheets.
Spread some of the minced meat on top, spoon over some bechamel sauce and cover again with lasagne sheets.
Continue in layers until all the ingredients are used up, finishing with lasagne sheets.
Top the lasagne with the sliced mozzarella and sprinkle with the Parmesan. Bake for 45-50 minutes until golden brown and bubbling. Remove and serve immediately.