1.Grind the onion and garlic in a food processor or mince very finely. In a small bowl mix sesame oil and curry together.
2.Heat the oil in a wok or a pot over medium heat. Cook the onion and garlic until fragrant (about 30 seconds). Add the curry mixture and cook, stirring frequently, for 30 more seconds. Add the broth and coconut milk and stir until the curry paste is mixed well. Add the sugar, salt, and white pepper. Adjust to taste.
3.Add the fish balls and cook, stirring occasionally until they are cooked through.
4.Add the cornstarch in water to the boiling sauce. Stir well and remove from heat. Serve hot with rice.