Whisk the eggs with the salt, then whisk in the warm stock. Warm, not hot. Hot stock scrambles the eggs, cold stock makes the custard steam unevenly.
Pour the mixture through a fine sieve into a wide heatproof dish. Straining removes the ropey bits of white that would otherwise show up as lumps.
Cover the dish tightly with foil or a plate. This stops condensation dripping from the steamer lid and pocking the surface.
Steam over the lowest simmer that still produces steam, 12 to 14 minutes, until just set with a slight wobble in the center. A hard boil curdles the custard into sponge; gentle heat is the entire trick.
While the eggs steam, heat the oil in a pan over high heat. Add the pork, press it flat, and let it brown undisturbed for 2 minutes before breaking it up.
Add the garlic, soy sauce, Shaoxing wine, and sugar to the pork. Cook another 2 minutes until the liquid reduces to a glaze.
Spoon the pork over the custard, drizzle with sesame oil, and top with scallions. Serve with rice, spooned straight from the dish.