In a mortar, pound white peppercorns until fine.
Add garlic and cilantro roots and continue to pound until fine.
Place chicken drumettes in a bowl, add the pounded spice mixture and dark soy sauce and toss to combine. Let marinate for 15-30 minutes while you prep other ingredients.
Add water to a pot and bring to a boil.
Drop the chicken drumettes (with all the juice and pounded spice mixture), potato and carrot in the pot and let cook for 15 minutes. Use a spoon to remove any excess fat from the top of the soup.
Add tomatoes and onions to the pot and simmer for 10 minutes.
Season with salt and adjust the taste as needed. Sprinkle with chopped Chinese celery to serve with rice or on its own.