In a large saucepan over medium-high heat, bring stock to boil. Meanwhile, in a medium bowl, soak bread in a small amount of cold water.
Heat oil in another large saucepan over medium heat. Add onion and sauté 3 minutes or until golden. Add garlic and sauté 1 minute. Add mushrooms and sauté 3 minutes or until they release their liquid. Stir in parsley.
Squeeze as much water as possible from bread and add to mushroom mixture. Add stock and nutmeg and bring to boil. Reduce heat and simmer, partially covered, 15 to 20 minutes.
Working in batches if necessary, transfer mushroom soup to a blender or food processor, cover and puree until creamy but still slightly grainy. Return to pan, add salt and pepper, and cook until heated through.