Mix eggs together but do not beat. Combine stock, both soy sauces and sugar in a saucepan. Bring to a gentle boil Add chicken and simmer, for 5 minutes. Add onion and simmer for 1 minute longer. Stir the eggs and pour in gently in a steady stream around the chicken. Let the egg spread naturally. Keep heat at medium until the eggs starts to bubble around the edges. Stir once and serve over rice. The egg should be slightly runny at this point as the rice will finish cooking the egg.