1
: In a small bowl or measuring cup, soak mushrooms in hot water for 20 minutes. Drain through fine cheesecloth or paper towel-lined sieve, reserving liquid. Chop mushrooms and reserve.
2
: In a large saucepan, melt butter over medium-high heat. Add onion and garlic and cook 2 minutes. Add sliced mushrooms and cook, stirring often for 6 to 8 minutes (there will be some moisture from the mushrooms). Stir in flour and cook for 3 minutes. Add reserved chopped mushrooms. Stir in stock, reserved mushroom liquid, thyme, salt and pepper. Stir in evaporated milk. Bring to a gentle boil. Reduce heat, cover and simmer for 20 minutes, stirring frequently.
3
: Purée soup with immersion blender or in food processor. Season to taste. Garnish with chopped parsley.