1. Fill a six-quart pot a bit more than halfway full with water and bring to a boil over medium heat.
2. Meanwhile, place ground chicken in a mixing bowl.
3. Using the S blade of your food processor, finely grind onion, celery, and carrot.
4. Combine the ground vegetables with the ground chicken. Add egg, hot water, sugar, and salt. Mix well.
5. Season the boiling water with the sugar, salt, and paprika.
6. Wet your hands and form balls out of the chicken mixture. Drop into the pot of boiling water.
7. Cover the pot, lower heat a bit and let chicken balls cook for 45 minutes.
8. Turn off heat and let cool. Using a slotted spoon, remove chicken balls from pot. Transfer to an airtight container and refrigerate. Serve cold.