Make the soup
Finely chop the fennel and the fresh rosemary leaves (removed from the stem). Wash the escarole,
spin-dry, then cut it crosswise into 1 cm strips. Set aside.
Heat half of the oil in a large saucepan over moderate heat. Add the fennel and rosemary, then cook, with stirring, until the
fennel is softened, about 5 min. Add the escarole, stir to coat it with oil, then cover and cook 2 min. Pour in the broth, then bring to a boil. Stir in the rice, then reduce the heat and simmer, covered, until al dente,
about 15 min.
Make the meatballs
While the soup simmers, put in a bowl the egg, nutritional yeast, ground meat and chives. Season with salt and pepper, then combine well. Form the mixture into meatballs about 2 cm in diameter (about 4 meatballs per serving).
Heat the remaining oil in a skillet over medium-high heat until hot but not smoking. Add the meatballs, then sauté until they are golden-brown on all sides, about 5-6 min.
Finish the soup
Transfer the meatballs to the soup, cover, then simmer
5 min.
Pour in the lemon juice into the soup. Adjust the seasoning, then serve the soup into pasta bowls.