Melissa Rubel cleverly uses chicken sausage here: removing the casings, shaping the meat into balls, browning them and simmering them in chicken broth. If you have leftover cooked rice on hand, feel free to substitute it for the orzo.
In a large saucepan of boiling salted water, cook the orzo until it is al dente, about 8 minutes. Drain and rinse the orzo under cold water until cool.
Meanwhile, in a medium soup pot, heat the olive oil until shimmering. Add the chicken meatballs and cook over moderately high heat until they are lightly browned, about 4 minutes. Using a slotted spoon, transfer the meatballs to a plate. Add the garlic to the pot and cook over moderate heat until lightly golden, about 1 minute. Add the chicken broth, bring to a simmer and season with salt and pepper. Add the meatballs to the broth and simmer until they are cooked through, about 3 minutes.
Add the baby spinach and cooled orzo to the simmering broth and cook, stirring, until the spinach is wilted and the soup is piping hot, about 1 minute. Ladle the meatball-and-orzo soup into shallow bowls and serve.