Chicken Orzo Soup

Name: Chicken Orzo Soup
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Cuisine: European, Mediterranean
Ingredients: 1 large yellow onion; 1 large or 2 small fennel bulbs; 2 cloves garlic; 2 tablespoons olive oil; 1 teaspoon kosher salt, plus more as needed; 1/4 teaspoon freshly ground black pepper; 2 (32-ounce) cartons low-sodium chicken broth (8 cups); 3 cups cooked and diced chicken (from about 1 rotisserie chicken); 3/4 cup dried orzo pasta; 1/2 head escarole; 1 tablespoon freshly squeezed lemon juice (from 1/2 lemon), plus more as needed