Halve pumpkin, remove skin and seeds and cut into small cubes.
Peel onion, garlic cloves and carrots. Finely chop the onion, press the garlic cloves and cut the carrots into fine cubes.
Wash the celery stalks under running water and cut into fine cubes.
Preheat oven to 200° Celsius.
Heat olive oil in a pan. Sautée the onions, garlic, carrots, celery and pumpkin for about 10 minutes.
Deglaze with white wine. Add the remaining ingredients for the pumpkin filling and simmer at low temperature until the liquid has thickened. The filling should not be too liquid, but rather compact.
Put the filling aside and prepare the bechamel.
Melt the margarine in a pan. Add flour and stir well until a yellow paste-like mass (Roux) is formed.
Add the vegetable milk and stir well with a whisk so that the roux can dissolve in the liquid.
Bring the béchamel to the boil briefly, then remove it from the hotplate or cook it over a very low heat until it has thickened. Flavour with salt, garlic powder and a little grated nutmeg. Mix in the yeast flakes.
Grease a casserole dish with a little margarine or oil. Spread a thin layer of pumpkin filling on the bottom. Followed by a layer of lasagna sheets (approx. 3 per layer).
Spread the lasagna leaves thinly with béchamel sauce.
Repeat steps 1 and 2 twice. Finish with a thicker layer of béchamel sauce.
Finally, sprinkle some more yeast flakes on the béchamel layer.
Bake the lasagne in the middle of the oven for about 30 minutes. Sprinkle with dried parsley before serving.