Cut chicken breast into chunks and transfer to a food processor. Add a pinch of salt, black pepper and cooking wine, then blend into a smooth, fine meat paste.
Scrape the paste into a mixing bowl. Add sugar, oyster sauce, light soy sauce, sesame oil, dried basil, egg white, water and cornstarch. Stir vigorously in one direction until the mixture turns thick, sticky and bouncy — this is the key to tender, springy meatballs that don’t fall apart.
Heat a small amount of oil in a pot over medium heat. Sauté ginger, garlic, green onion and diced purple onion until fragrant.
Add diced fresh tomatoes and tomato paste. Stir-fry over high heat until tomatoes break down completely and release their natural juice.
Pour in 3 bowls of water and add 1 teaspoon of sugar. Bring to a near-boil, then lower heat to a gentle simmer to prevent meatballs from breaking apart.
Scoop the meat paste with a spoon and shape into small balls, dropping them one by one into the simmering soup. Turn heat back to high once all meatballs are in the pot.
Cook until the sauce reduces to a glossy, thick coating. Season with a final pinch of salt, then serve. Pair with a small portion of brown rice for a balanced weight loss meal.