How to make
Boil the cauliflower and onion in salted boiling water. Boil the spinach and discard the water.
Melt the butter. Fry the flour in it. Beat well, so that no lumps remain. Pour the milk in a thin stream.
Leave it to cool slightly and blend the vegetables along with the milk sauce in a blender.
If you feel like it's too thick, add a little of the water in which you have boiled the cauliflower. Season with black pepper and salt, if necessary.
Serve it with croutons, nuts or something crunchy of choice.