How to Make It
In a large heavy pot, heat the oil over medium heat until hot. Brown the chicken, in batches if necessary, transferring the chicken to a plate as browned, about 6 minutes per batch. Stir the onions, carrots, celery, 3/4 teaspoon salt, and 1/2 teaspoon pepper and cook, stirring occasionally, until golden, about 8 minutes. Stir in the chicken with any accumulated juices and the stock, and bring to a gentle boil. Cook the soup, stirring occasionally, until the chicken is cooked through, about 20 minutes.
Stir in the pasta and cook until al dente. Season the soup with salt and pepper to taste and serve.