Note: Once this custard is cooked and solidified, remove from the steamer and do not return to the steamer or the custard will liquefy. Beat eggs in bowl. Beat in 1 teaspoon of salt, rice vinegar, oyster sauce and stock. Place bowl on a rack in a pot or steamer. Cover and steam over boiling water 20 minutes. Set custard aside until ready to serve.
Heat 2 tablespoons of oil in wok. Add scallion, ginger, and pork. Stir-fry for 2 minutes. Add soy sauce. Cook 1 minute more and remove from heat. Mix cilantro and shrimp with 1/4 teaspoon salt and cornstarch. Stir-fry shrimp in 1 tablespoon heated oil 2 minutes. Add pork mixture and stir-fry 30 seconds more.
Invert custard onto platter. Pour pork and shrimp mixture over custard.