Preheat the oven to 200°C.
Roast the chicken on a rack over a tray for 15-20 minutes until golden.
Place chicken in a pan with diced vegetables, bouquet garni, water, and seasoning.
Simmer for 40-45 minutes until the chicken is tender.
Remove chicken, shred the meat, and reserve the roasting fat.
Strain stock through a sieve into a clean pan and discard boiled vegetables.
Whisk minced chicken and egg whites into the stock and bring slowly to a simmer to clarify.
Strain the clarified stock through a fine sieve once more.
Blanch leek strips in boiling salted water for 1-2 minutes then refresh in ice water.
Assemble bowls with shredded chicken, leeks, and prunes then ladle warm stock and chicken fat over.