In a large stockpot, heat the vegetable oil over medium-high heat. Add the chicken bones, stir to coat and cook for 5 minutes to brown. Add the vegetables to the stockpot along with the herbs and peppercorns. Stir to mix, add the water and bring to a simmer. Reduce the heat to medium and let simmer for 4 to 6 hours. The stock will have reduced by half. Strain and skim the fat. Adjust the seasoning with salt and pepper. Reserve.
For the chicken meatballs:
Soak the breadcrumbs in the milk. In a food processor, combine the ground chicken, or chicken breasts if using, the red onion and garlic. Blend for 2 minutes. Add the dill, olive oil, salt, chile flakes and breadcrumb mixture. Spinkle with freshly ground pepper.
Using 1 teaspoon of the ground chicken mixture, form small meatballs. Reserve on a baking sheet lined with parchment paper, cover with plastic wrap and keep in the refrigerator until ready to cook in the soup.
For the soup:
In a medium stockpot, cook the vegetables in oil for about 2 minutes. Season with salt and pepper. Add 8 cups stock and the chicken meatballs. Let simmer until the meatballs are cooked, about 15 minutes. When ready to serve, divide the watercress in the bowls and add a ladle of chicken soup. Garnish with the blackened chicken wings and fresh dill.