Blanch the asparagus in boiling salted water for 3-4 minutes, adding the lettuce leaves for the last minute. Drain.
Heat one tablespoon of the sesame oil in a frying pan and fry the prawns for two minutes, or until they turn pink all over.
To serve, arrange the asparagus and lettuce on a serving plate. Place the prawns on top and sprinkle over the chilli. Drizzle with the remaining tablespoon of sesame oil and the soy sauce.