Preheat the oven to 175 degrees Celsius or 340 degrees Fahrenheit.
Roll out the puff pastry and place it with a baking paper on a baking sheet. Overlap the edges once to the inside of the rectangle.
The lower ends of the asparagus (about 2 cm) are cut away because they are very woody and tough. Then peel the asparagus carefully (it can break easily): place the asparagus on an upside down pot and peel it gently while it is lying there. The white asparagus is peeled just from below the tip of the asparagus downwards, the green asparagus only needs to be peeles on the lower third.
Prepare the béchamel sauce: heat the milk in a saucepan with salt, pepper, bay leaf and nutmeg. Melt the margarine in another pot, then add the flour to that pot. Simmer constantly with the whisk and pour the hot milk into the margarine flour mixture after 3 minutes. Let it simmer slightly for 5 minutes while stirring.
Use a kitche palette to spread the vegan béchamel sauce evenly on the puff pastry. The up-sided edges of the dough ensure that nothing runs out.
Now put alternately a green and a white asparagus on the tart. Leave 2 cm free between the asparagus. Scatter the vegan cheese over the tart.
Bake the vegan asparagus tart in the oven for 30-35 minutes and enjoy it best with some freshly grated lemon zest.