For the sauce, mince the garlic and grate the ginger into a bowl. Stir in the ketchup, gochujang, soy sauce, rice vinegar and sesame oil. Chill until ready to serve.
For the cauliflower, preheat the oven to 425°F (220°C) and line a baking tray with parchment paper, or heat your Air Fryer to 350°F (180°C).
Cut the cauliflower into large florets (3 to 4 cups/750 mL to 1 L) and place in a large bowl.
In a separate bowl, whisk the rice flour, potato starch, sesame seeds, soda water, oil and salt. Pour this over the cauliflower and toss well to coat.
Spread the battered cauliflower in a single layer on the baking tray and bake for about 25 minutes, until you see a little browning. If using an Air Fryer, you may need to do this in batches.
In a clean large bowl, toss the cauliflower with half of the sauce and then return it to the tray to bake for an additional 10 to 15 minutes, until browned.
Transfer the cauliflower to a serving dish, sprinkle with green onions and serve with the remaining sauce for dipping.
