In a wok on high heat, put the oil, and wait until hot. Add the ginger, press it down, and wait a few moments, until it becomes fragrant. Add the broccoli, stir very rapidly for 5 seconds, then turn the heat down to medium-high, and stir until the flowerets are a bright, shiny green.
Add the salt and the sugar, stir rapidly, then add the stock.
Cover, and cook on medium-high heat for 2:30 minutes.
Uncover, and cook, stirring rapidly, until all the liquid is gone. Then dribble the sesame oil on top of the broccoli, give them a few tumbles with the spatula to distribute the oil equally across the broccoli.
Serve hot, at room temperature, or cold (we like ours hot, usually with dishes that are heavy or with strong tastes, which covers pretty much 90% of Vietnamese dishes :D).
Notes
Remember to fish out the ginger before you serve it! (grated ginger is OK, but an entire nub of ginger can be a bit of a surprise to find down one's throat, as the H can attest).
Recipe by Aliette de Bodard at https://www.aliettedebodard.com/recipes/best-stir-fry-broccoli-recipe-ever/