-
1
Prepare a charcoal grill and bring it to high heat, then pat the steak dry so the surface sears immediately rather than steaming and losing colour. Grill directly over the coals, turning once, until the exterior carries a pronounced char and the internal temperature reaches 55–58 °C. The surface should be deeply coloured and the juices visibly beading at the surface — this is the waterfall the dish is named for.
-
2
Remove the steak from the grill and rest it uncovered for 5 minutes so the juices that have been driven toward the centre by the heat redistribute evenly through the meat; cutting now would lose them to the board rather than to the dressing. Leave it uncovered rather than tented, so the crust does not steam soft.
-
3
While the steak rests, combine the lime juice, fish sauce, palm sugar, and dried chilli flakes in a bowl, stirring until the palm sugar dissolves so its sweetness is evenly present in every mouthful rather than pooled at the bottom. Taste the dressing: it should read sharp, salty, and warm with chilli in that order; adjust lime or fish sauce if the balance is off.
-
4
Slice the rested steak thin against the grain so each piece is tender to the bite rather than pulling, and do it immediately so the slices are still warm to the touch — not at room temperature. Slices left to cool on the board will no longer carry enough heat to open the dressing and wake the aromatics.
-
5
Transfer the warm slices directly into the dressing, add the shallot rings and khao khua, and toss immediately so the residual heat of the meat briefly softens the shallots and blooms the toasted rice powder, releasing that characteristic smoky, nutty fragrance. The combined smell at this moment should be simultaneously smoky, sour, and herbaceous — neither raw dressing nor plain grilled beef alone.
-
6
Add the mint and sawtooth or fresh coriander and toss once more, working quickly so the herbs meet the warm meat without wilting in it. Plate and serve at once — the herbs should stand fresh and upright on the dish.