Mushroom Tortellini and Escarole Soup

Ingredients

 * 2 tsp olive oil
 * 1 small onion, finely chopped ( ½ cup)
 * 3 shiitake mushrooms, sliced ( ½ cup)
 * 7 cups vegetable broth
 * 5 cups chopped escarole
 * grated Parmesan cheese (optional)
 * cooked tortellini

Directions

 * 1) In large pot, heat oil over medium heat.
 * 2) Add onion and mushrooms and cook, stirring often, until softened, about 3 minutes.
 * 3) Add vegetable broth and heat through.
 * 4) Add escarole and cook 2 minutes.
 * 5) Add cooked tortellini and heat through.
 * 6) Serve with parmesan cheese if desired.