Clean cauliflower and remove the outer leaves. Cut cauliflower into florets, rinse with water and drain well. This is a crucial step as you don't want the excess water to dilute the batter.
To prepare the cauliflower, mix the batter ingredients in a large mixing bowl until well combined. Then, dip florets into the batter and air-fry in a preheated air-fryer at 390°F (200°C) for 8-10 minutes until golden brown, with a shake in between.
In heated non-stick pan, toast peppercorns for 30-45 seconds, then let it cool down.
Transfer to a mortar and pestle and pound them into tiny bits. Alternatively, use a spice grinder or small food processor to crush the peppercorns. See Notes for crushed peppers.
To make the black pepper sauce, add a tablespoon of oil in a preheated non-stick pan, then sauté shallots until translucent, and continue to cook the garlic until fragrant.
Add in the butter and let it melt, then continue to add the add chilies, curry leaves, and crushed peppercorns.
Stir until well combined and season with soy sauce, sugar, and vegan 'oyster' sauce. Add the cauliflower florets and toss until well combined.
Garnish with chopped green onions and more chilis, then serve warm.