Prepare all of the ingredients including peeling and de-veining the prawns if raw.
Mix the cornflour and water together and then add all ingredients to a small saucepan and mix well.
Bring the pan to the boil over a low-medium heat making sure the mixture does not boil over. Boil for 1 minute and then set aside for 10 minutes
Once cooled a little pour half of the teriyaki sauce over the prawns.
Stir the prawns and teriyaki sauce together and set aside for 10-20 minutes.
Next, add the spring onions to a frying pan over a medium to high heat fry for 1-2 minutes, Now, add the prawns and the rest of the teriyaki sauce. Cook for 2-3 minutes or until the prawns are cooked through.
Finally, serve in lettuce wraps and garnish with chopped spring onion and sesame seeds.