Preparation Blanch onions in a saucepan of boiling water 2 minutes. Drain; cool. Peel onions. Heat oil in heavy large skillet over medium-high heat. Add garlic and sauté 1 minute. Add water, celery, fennel, and onions; bring to boil. Add mushrooms, vinegar, salt, pepper, and coriander. Simmer mushrooms until tender, about 30 minutes. Pour mushroom mixture into strainer set over large bowl. Return strained liquid to same skillet. Boil until reduced to 1/2 cup, about 12 minutes. Combine mushroom mixture and reduced liquid in large bowl. Mix in parsley and thyme. Chill at least 2 hours and up to 6 hours. Arrange watercress around edge of platter. Mound mushroom mixture in center. Sprinkle with cheese and serve.
Preparation Blanch onions in a saucepan of boiling water 2 minutes. Drain; cool. Peel onions. Heat oil in heavy large skillet over medium-high heat. Add garlic and sauté 1 minute. Add water, celery, fennel, and onions; bring to boil. Add mushrooms, vinegar, salt, pepper, and coriander. Simmer mushrooms until tender, about 30 minutes. Pour mushroom mixture into strainer set over large bowl. Return strained liquid to same skillet. Boil until reduced to 1/2 cup, about 12 minutes. Combine mushroom mixture and reduced liquid in large bowl. Mix in parsley and thyme. Chill at least 2 hours and up to 6 hours. Arrange watercress around edge of platter. Mound mushroom mixture in center. Sprinkle with cheese and serve.