Mix chicken, egg, breadcrumbs, Parmesan, half the garlic, 1/2 teaspoon salt and pepper just until combined. Roll into 32 small meatballs, each about 1 inch across.
Heat oil in a 6-quart pot over medium heat. Cook onion and carrots for 5 minutes, then remaining garlic for 30 seconds.
Add broth and remaining salt, cover and bring to a gentle simmer. Lower meatballs into the broth one at a time and simmer gently for 5 minutes.
Stir in pearl couscous and simmer for 10 to 12 minutes, stirring carefully between meatballs, until couscous is tender and the largest meatball reaches 165°F.
Add escarole and simmer for 2 to 3 minutes until tender. Stir in lemon juice and divide among 6 bowls.