Peel the prawns and reserve the shells.

Butterfly the prawns by cutting a deep slit in the back of the prawns, removing the intestine and flattening the prawn meat.

Combine the prawn shells with about 1.5L of water in a small saucepan and bring to a simmer. Simmer for 15 minutes, then strain and discard the shells, reserving the stock.

Mix the prawn meat with 2 tbsp of cornflour and ½ a cup of cold tap water. Rub the prawns in the cornflour mixture and set the prawns aside for at least 15 minutes.

Place the oil into a large saucepan and heat to 175C. Remove the prawns from the cornflour mixture and add to the hot oil. Deep fry the prawns for about 2 minutes until nearly cooked through, then remove and drain.

Heat a large wok over medium heat, add the butter and the garlic. Fry the garlic for about 1 minute until fragrant but not yet browned.

Add about 2 tbsp of the prawn stock, the fish sauce, Shaoxing wine and a generous pinch of sugar. Add the prawns and toss through the garlic butter sauce.

Mix a little extra cornstarch with some cold water and add a little to the sauce to thicken.

Remove the prawns and sauce to a plate to serve.