Combine dried mushrooms and 1 cup of the water in a 2-cup glass measure. Microwave, uncovered, on 100 percent power (high) for 3 minutes or until boiling. (Or, pour 1 cup boiling water over dried mushrooms.) Let stand for 10 minutes. Drain mushrooms, reserving liquid; finely chop.
Cook onion and the fresh mushrooms in a medium saucepan in margarine or butter until tender but not brown. Stir in drained mushrooms, reserved liquid, remaining 2 cups water, pumpkin, bouillon granules, nutmeg, salt, and pepper.
Cook and stir over medium heat until heated through. If desired, garnish with chives and additional mushrooms; top with a little warm cream. Makes 6 to 8 servings.