Prep the bread: Use slightly stale bread if you can. Trim the crusts for neat edges, or keep them on for extra crunch.
Cut each slice into triangles (2–4 per slice depending on size).
Make the prawn paste: Pat the prawns dry. In a food processor, pulse the prawns with garlic, ginger, soy sauce, sesame oil, sugar, pepper, and egg white (if using) until you have a thick, slightly chunky paste. Stir in most of the spring onions, saving a pinch for garnish.
Spread the mixture: Divide the prawn paste evenly among the bread triangles, spreading it right to the edges so it adheres during cooking.
Aim for a layer about 5–7 mm thick.
Add sesame seeds: Pour sesame seeds into a shallow dish. Press the prawn side of each triangle gently into the seeds to coat the surface.
Preheat the air fryer: Set to 190°C/375°F for 3 minutes. Lightly brush the air fryer basket or tray with oil to prevent sticking.
Brush with oil: Lightly brush or spray the sesame-coated prawn side with oil.
This helps the seeds toast and the top crisp up.
Air fry in batches: Arrange toast pieces prawn-side up, spaced slightly apart. Cook for 6–8 minutes, until the sesame seeds are golden and the prawn mixture is firm and opaque. Thicker pieces may need an extra minute.
Check doneness: The prawn layer should be fully cooked through (no translucency), and the bread edges should be crisp.
If the tops are browning too fast, reduce the temperature to 180°C/360°F and continue for another minute.
Serve: Sprinkle with reserved spring onions. Add a squeeze of lime or lemon and serve hot with sweet chili sauce, soy-chili dip, or a simple ponzu.