Prepare the sauce ahead of time by combining all the ingredients for it in a small saucepan and adding 50ml of water. Bring to a simmer over a low heat, stirring to help dissolve the sugar. Remove from the heat once thickened to the consistency of tomato ketchup.
Reserve to one side. Combine half of the groundnut oil, red chilli, ginger and garlic in a small bowl, stirring until smooth.
Make a few diagonal slashes in the skin and flesh of both sides of the sea bream. Rub the paste into the slashes. Heat the remaining groundnut oil in a large fish pan over a moderate heat. Fry the sea bream, turning occasionally, for 14-18 minutes, until the flesh is cooked and the skin is crispy all over.
Reheat the sauce towards the end of cooking time. Arrange the fish on a serving platter and spoon the sauce to one side of it. Garnish with a few basil leaves before serving.