To make easy mushroom soup, heat mushrooms, chicken broth, beef broth, onion, carrots, black pepper, peas, rosemary and celery in a 4-quart saucepan over medium heat and bring the ingredients to a boil. Reduce the heat to low, and cover the ingredients to cook for 15 minutes. Add green onions and continue cooking for five more minutes until the vegetables tenderize.
When cooking a simple mushroom soup, gather 1 pound firm white mushrooms, a medium lemon, a tablespoon unsalted butter, 2 tablespoons minced shallots and 1/4 teaspoon dried thyme. Ensure you also have 1/2 bay leaf, one teaspoon salt, 1/2 teaspoon freshly ground pepper, 2 cups heavy cream, 1 1/2 cups chicken stock and a teaspoon cornstarch.
Sprinkle lemon juice over the mushrooms and chop them coarsely. Melt the butter in a 4-quart saucepan and saute the shallots lightly. Add the mushrooms and other vegetables such as peas, carrots, rosemary, thyme and celery, and cook for 10 minutes or until the liquid disappears.
Add chicken broth, beef broth, pepper and salt and bring the ingredients to a boil. Moderate the heat and simmer for 20 minutes. Add cornstarch and green onions and continue simmering for five more minutes while stirring the soup. Season the soup to taste and serve.