Gently cook the sliced onions in the margarine without colouring.
Mix in the flour, cook over a gentle heat to a sandy texture without colour.
Remove from the heat, cool slightly.
Add the well washed, chopped mushrooms, bouquet garni and seasoning.
Gradually mix in the hot stock. Stir to the boil.
Simmer for 30 minutes. Skim when needed.
Remove the bouquet garni, liquidise.
Pass through a chinois, return to a clean pan.
Re-boil, correct the seasoning and consistency and add the milk.
