Remove stems from cilantro, and coarsely chop leaves.
Process cilantro and 1 cup chicken broth in a blender or food processor until blended, stopping to scrape down sides.
Melt butter in a Dutch oven over medium heat; whisk in flour. Gradually add remaining 3 cups broth, whisking constantly until mixture is smooth. Boil 1 minute. Stir in cilantro mixture, cream cheese, and next 5 ingredients; simmer soup 15 minutes. Garnish, if desired.