Crack the Eggs into a mixing bowl and whisk gently until the whites and yolks are fully combined and slightly frothy.
Slowly whisk in warm Anchovy-Kelp Stock — a ratio of roughly 1 part eggs to 1–1.5 parts stock works well — until the mixture is smooth and uniform.
Season the mixture with a pinch of Sea Salt and a small splash of Fish Sauce, tasting lightly and adjusting to preference.
For the silkiest texture, strain the egg mixture through a fine-mesh sieve into a heatproof, shallow bowl to remove bubbles and any stringy bits.
Set the bowl into a pot with an inch or two of simmering water (or place in a steamer), cover with a lid, and cook over low heat until the custard puffs and is just set — about 10–15 minutes depending on depth.
When the eggs are nearly set, remove the lid, drizzle a little Toasted Sesame Oil over the surface and sprinkle with thinly sliced Green Onion; cover again for a minute so the aromatics bloom.
Serve the gyeran jjim hot, straight from the bowl, enjoying its tender, custardy texture.
