Wash and peel the white asparagus and cut off the woody lower ends. Wash the green asparagus and also cut off the woody lower ends. Cut the asparagus into slices. Peel and finely chop the onion.
Peel the garlic and also dice finely. Heat oil in a pot, fry onion and garlic in it until transparent, add broth and bring to the boil. Add asparagus and cook for 8-10 minutes. Season stock to taste with salt, pepper, sugar and soy sauce.
In the meantime, heat olive oil in a pan and roast the slices of bread in it for 1-2 minutes on both sides. Arrange the soup and a slice of bread in soup bowls. Serve garnished with chervil as desired.