Blanch Asparagus: Cook the asparagus in boiling salted water for a few minutes until tender. Drain and immediately transfer to iced water to keep them green.
Prepare Béchamel Sauce: In a saucepan, melt butter. Add flour and whisk well. Slowly pour in the soy milk (or vegetable drink) while stirring continuously to avoid lumps. Add salt and nutmeg. Cook until the sauce thickens.
Make Asparagus Cream: Reserve the asparagus tips. Roughly chop the remaining asparagus and blend with some water, oil, salt, pepper, and part of the béchamel sauce until smooth.
Toast and Chop Walnuts: Toast the walnuts until fragrant, then chop them roughly.
Assemble Lasagna: In a 25 cm square baking dish, brush a little oil on the base. Spread a layer of asparagus cream béchamel, then place a layer of carasau bread (don’t worry if it breaks). Add more asparagus cream béchamel, some classic béchamel, asparagus tips, walnuts, parmesan, and slices of brie.
Add Second Layer: Repeat the layering with asparagus cream béchamel, classic béchamel, asparagus, walnuts, grated parmesan, and brie slices.
Add Final Layer and Bake: Finish with a drizzle of oil on top. Bake in a preheated oven at 200°C (392°F) for 10-15 minutes. Then switch to grill mode for a few minutes to brown the top.
Serve: Let the lasagna cool slightly before serving.