Add broth, beans, tomatoes and red pepper flakes and bring to boil on high heat.
Reduce heat to medium-low. Cover and simmer until escarole is tender and flavors blend, about 20 minutes.
Season soup to taste with salt and pepper.
Serve with a sprinkle with Pecorino-Romano or Parmesan cheese.
Notes
* Soup freezes well. Let cool and place in freezer-safe containers. * If you have a cheese rind (from Parmesan cheese or another hard cheese), add it to the soup when you add the broth, beans, etc. It will melt into the soup and give it some extra cheese flavor.