-
1
Kill the crabs immediately before preparation, then remove the top shell, discard the gills, and rinse the body cavity under cold running water — the gills carry a muddy bitterness that would cloud the finished brine. Pat dry and arrange the crabs in a deep, non-reactive container, stainless steel or food-grade ceramic, large enough to hold them in a single close layer. The crab is ready when all surfaces are clean and the roe (게란 내장) is visible as an intact orange-coral mass inside the body.
-
2
Combine the ganjang, water, garlic, chilli, ginger, and sesame in a saucepan and bring to a full boil over high heat, then remove from the heat, so the garlic and ginger release their fragrance into the brine rather than staying raw and sharp against the crab. Allow the brine to cool completely to room temperature, then refrigerate until cold — it must read below 4 °C before it touches the crab. The brine is ready when it smells of sharp, clean soy with garlic riding just behind it.
-
3
Pour the cold brine over the crabs until fully submerged, weighting with a small plate if necessary to keep every surface beneath the surface, so no exposed flesh oxidises or dries unevenly during the cure. Cover the container and refrigerate at or below 4 °C for 24 hours. This is where the dish lives or dies: the marinating temperature must never deviate above 4 °C, and the crab must have been live or just-killed — any compromise on either condition renders the preparation unsafe and the dish is lost.
-
4
After 24 hours, drain the brine from the crabs into the saucepan and return the crabs to the refrigerator while you work, so they are never left to warm. Bring the drained brine to a full boil, skimming any foam that rises — skimming keeps the brine clear and prevents any off-flavour from the proteins drawn out of the crab accumulating in successive cycles. Remove from the heat, cool completely, refrigerate until cold, then pour the re-boiled brine back over the crabs; cover and refrigerate. The brine will have deepened in colour and thickened slightly — this concentration is correct.
-
5
Repeat the drain-reboil-cool-re-pour cycle two to three more times over successive days, for a total marinating period of 3–7 days, so each pass drives the brine deeper into the flesh and cavity rather than leaving the cure concentrated only at the surface. At 3 days the crab flesh will be translucent, lightly set, and deeply saline; at 7 days it will be more fully cured throughout. The roe should be soft, creamy, and paste-like — this is the marker of a properly marinated ganjang-gejang.
-
6
Serve the crab cold, directly from the refrigerator, alongside a bowl of plain cooked short-grain white rice. The crab's soy-marinated juices are mixed grain by grain into the rice at the table. Consume within 7–10 days of the initial pour; beyond this point the flesh softens past the point of correct texture.