Pat the fish fillets dry with paper towels, remove any remaining bones and skin. Cut the fish into 1-inch pieces and place in the freezer for 10–15 minutes until just beginning to firm but not frozen solid—this helps with grinding.

Pulse to a paste

Working in small batches if necessary, place chilled fish pieces into a food processor. Pulse until the fish breaks down into very small pieces, then scrape down the bowl. Add the ice water and egg white and process in short bursts until the mixture turns smooth and slightly sticky (a fish paste or forcemeat). This should take about 1–2 minutes total of processing.

Incorporate binders & seasonings

Transfer the fish paste to a chilled bowl. Add cornstarch, salt, white pepper, and sugar. Fold or knead the paste with a spatula or spoon for 1–2 minutes to develop the slightly elastic texture. If using, add chopped green onion, ginger, and soy sauce and mix until evenly distributed.

Shape the balls

Fill a medium bowl with cold water and add 1 tablespoon vegetable oil (this keeps the fish from sticking to your hands). Wet your hands, scoop about 1 tablespoon of fish paste, and use a wet thumb-and-forefinger method (or a spoon-and-scoop) to form compact balls roughly 1 inch (about 3/4–1 tablespoon paste each). Place formed balls on a tray lined with parchment or on a lightly oiled plate. Continue until all paste is used, periodically wetting hands.

Chill before cooking (optional)

For best texture, chilling the shaped fish balls in the refrigerator for 20–30 minutes helps them hold shape when poaching.

Cooking / serving

Bring broth to a simmer

In a wide pot, bring the chicken or fish broth to a gentle simmer over medium heat. Do not boil rapidly—small bubbles simulating a poach are ideal. If you prefer clear poaching liquid, skim any foam that rises.

Poach the fish balls

Carefully drop the chilled fish balls into the simmering broth in batches so they have room. Stir gently once to prevent sticking. Cook at a gentle simmer until the fish balls float and are firm to the touch, about 5–7 minutes depending on size. Check one by cutting it in half—the center should be opaque and springy.

Shock in ice bath (optional for firm texture)

If you want extra-firm, bouncy fish balls (common in many Asian preparations), transfer cooked balls with a slotted spoon to a bowl of ice water for 1–2 minutes, then return to warm broth or serve chilled, depending on the dish.

Serve

Serve fish balls in the simmering broth as soup, add to noodle bowls, or present with dipping sauce on the side. Garnish with chopped green onion or sesame oil if desired.