Make the meatballs. Place the ground pork, minced scallion bottoms, egg white, 1 tablespoon of the fish sauce, 2 teaspoons of the ginger and all of the salt and pepper.

Gently mix to combine. Then line a small sheet pan or platter with parchment and spray slightly with pan spray. Divide the mixture into 16 and gently roll into meatballs. (Gently is the key, just toss between wet hands until round).

Place on the sheet tray and refrigerate for 30 minutes to firm up.

While the meatballs are chilling, start the soup.

In a 3-4 quart pot, heat oil over medium heat and add the onions and saute for two minutes.

Add the garlic and remaining 2 teaspoons of ginger and saute for two more minutes.

Add lime juice and cook one minute, then add chicken stock and remaining two tablespoons of fish sauce.

Bring to a simmer and simmer gently until the onions are tender, about ten minutes.

After 30 minutes, remove the meatballs from the refrigerator and carefully lift and drop one at a time into the simmering soup.

Increase heat until bubbling then lower again to a simmer and simmer about 20 minutes until meatballs are cooked through and tender.

Add the watercress, stir, remove from heat and serve with the scallion greens minced over the top of each portion.