Rub the salt and baking powder, if using, into the prawns. Leave to marinate for 10 minutes.
After 10 minutes, rinse the prawns and dry them.
Save the prawn shells in the freezer, and use it to make a seafood stock another time.
In a wok over high heat, add the vegetable oil.
Saute the chopped garlic and dried chilli until fragrant, then add the prawns.
When the prawns begin to cook, add the Shaoxing wine, if using.
Stir in the soy sauce, sugar and sesame oil.
When the prawns are cooked through, stir in the cornstarch solution and cook to thicken.
Stirring the basil in at the end retains its fragrance, but for extra freshness, garnish with more fresh basil after plating.
Stir the basil leaves in, and serve immediately.