Separate the cauliflower into flowerets, trimming overly long stems. Leave the smaller ones intact; cut the larger ones in half so they're all about the same size. Rinse and drain. (But do not dry -- you want some moisture on the cauliflower.).
Heat a wok or large skillet over high heat until hot; turn heat to medium. Add the oil, swirl and heat for about 15 seconds.
Add the flowerets; stir quickly to coat them with oil, then sprinkle in the salt and stir briefly.
Add the stock, making sure all of the stems are down in the liquid. When it boils, cover and simmer vigorously for 5 to 10 minutes (depending on the size of your flowerets) until tender.
In the meantime, slice the scallions thinly.
Uncover the cauliflower, turn heat high and stir gently but rapidly until there is just a little foaming liquid in the skillet. Toss in the scallions; add the teaspoon of sesame oil. Stir gently to distribute scallions and sesame oil throughout.