- Heat the butter in a heavy sauce pot or pan, add chopped onion and mushroom stir for few seconds until just transparent. Don't let the mushroom brown.
- Then add flour, stir to make roux. Don't let them brown, then pour over milk or white stock, bring to boil.
- Simmer the soup for 10 to 15 minutes until mushroom is cooked.
- Pass the soup through a food mill or into a blender to purée it.
- Add the purée of mushroom into the soup and add enough hot milk or cream to the soup to bring it to proper consistency but do not boil.
- Season to taste, garnish with brunoised mushroom and parsley.