Wash and dry the cauliflower. Break or cut it into small florets. I like them smaller than bite sized so that they cook through faster.
It’s best to stir fry the cauliflower in a single layer so if it doesn’t all fit, work in batches.
Heat the oil in a large pan or wok over medium heat. Add the cauliflower and leave to fry undisturbed until browned on the first side - about 5 minutes.
Stir and flip the cauliflower to another side and allow to fry until browned. Continue until the cauliflower is tender in the middle.
(If it is charring too quickly before it is cooked through the middle, add one or two tablespoons of water to the pan and the lid to steam through. Allow the water to simmer off before adding the stir fry sauce).
While the cauliflower is frying, combine all the remaining ingredients for the sauce and stir well to dissolve the cornstarch.
Add the sauce to the cauliflower and stir continuously until the sauce thickens and coats the cauliflower - about 2 minutes.