Sprinkle the mushrooms with lemon juice. In a food processor, coarsely chop them.
Melt butter in a large soup pot over medium-high heat; cook mushrooms in butter with 1 pinch salt until the mushrooms release all the juices; reduce heat to low. Continue to cook, stirring often, until juices evaporate and the mushrooms have to bean golden brown, about 15 minutes. Set aside a few attractive mushroom slices for garnish later, if desired. Mix onion with the mushrooms and cook until onion is soft and translucent, about 5 more minutes.
Stir flour into mushroom mixture and cook, stirring often, for 2 minutes to remove the raw flour taste. Tie thyme sprigs into a small bundle with kitchen twine and add to mushroom mixture; add garlic cloves. Put the chicken stock and water into mushroom mixture. Bring to a simmer and cook for 1 hour. Remove thyme bundle
Add the cornstarch to the soup and continue to simmer 10 minutes longer, stirring constantly. Correct seasoning to taste.
Serve in warm bowls. Sprinkle with minced parsley
- 1 pound firm white mushrooms
- 1 lemon
- 1 tablespoon butter
- 2 tablespoons shallots
- 1/4 teaspoon dried thyme
- 1/2 leaf
- 1 salt
- 1/2 teaspoon pepper
- 2 cups cream
- 1 1/2 cups chicken stock
- 1 teaspoon cornstarch, dissolved in 1 tablespoon of water
- 1 tablespoon parsley