This is a great, easy chicken-and-rice soup. We like to use instant brown rice because it cooks so quickly, but you could substitute cooked brown rice (stirred in at the end) if you have it on hand. Try the recipe with other herbs if you like, such as dill or tarragon.
Heat oil in a large saucepan over medium heat. Add carrots, onion and celery and cook, stirring, until beginning to soften, 3 to 5 minutes. Add broth and bring to a boil. Add rice, reduce heat and simmer for 5 minutes. Add chicken and peas and gently simmer until the chicken is just cooked through, about 5 minutes. Stir in parsley, vinegar and pepper.