Use a fine mesh sieve to rinse one cup of pearl barley under running water until clear, then transfer to a soup pot. Pour in the chicken stock, stir, bring to a boil then reduce heat.
To a flat-bottomed wok or pan, heat olive oil, fry the diced onion, carrot and celery over low heat for around 10 minutes, add garlic and continue to fry until fragrant, taking care to brown but not burn the garlic.
Transfer to the soup pot, add the leftover rotisserie chicken pieces (or shredded poached chicken breasts), spices and seasoning, and continue to cook until the chicken has warmed up and the barley has expanded, and you have a dense soup with a porridge-like consistency.
Taste, adjust the spice or seasoning to suit your palate. Just before serving, stir through the fresh herbs, spoon on a dollop of sour cream, and serve with slices of crusty sourdough, pickles and more fresh herbs.