Finely chop sliced mushrooms and 4 ounces shiitake mushrooms, or pulse mushrooms in a food processor 5 or 6 times.
Sauté finely chopped mushrooms, onion, and garlic in 2 tablespoons butter in a large saucepan over medium-high heat 8 minutes or until tender. Add wine; simmer 3 minutes or until wine has almost evaporated.
Combine flour and 1/2 cup broth, stirring until smooth; add to soup. Stir in remaining 3 1/2 cups broth, salt, and pepper. Bring to boil; reduce heat, and simmer, uncovered, 10 minutes. Stir in whipping cream. Return soup to a boil; reduce heat, and simmer 1 minute. Remove from heat.
Sauté chopped oyster mushrooms and 1 cup shiitake mushrooms in remaining 1 tablespoon butter in a large skillet over medium-high heat 3 to 5 minutes or until golden; stir into soup. Season to taste with freshly ground pepper.