First, make the sauce. Put the orange juice, sugar, tomato purée, ketchup and vinegar in a large saucepan over a medium heat. Bring to the boil, then reduce the heat and simmer for 5 mins. Slowly pour in the cornflour mixture, a little at a time, stirring continuously until you have the desired consistency. Remove from the heat and set aside.

Mix the flour, baking powder and 1 tsp salt together in a large bowl. Beat the eggs, milk and 1 tbsp oil together in a separate bowl. Pour the wet ingredients into the dry and mix well to create a smooth paste. Add the chicken pieces and mix, making sure each piece is thoroughly coated.

Fill a deep saucepan or wok no more than a third full with oil and heat to 170C, or until a cube of bread dropped in browns within 30 seconds. Carefully lower the coated chicken pieces into the oil, one piece at a time, and fry in batches of five for about 5-6 mins each batch until golden brown and cooked through. If you have a food probe thermometer, the internal temperature should reach 78C. If you don't have a thermometer, cut a chicken piece in half to ensure the juices run clear.

Drain the fried chicken on a wire rack set over a baking tray lined with kitchen paper, or on a plate lined with kitchen paper. Serve with the sweet & sour sauce for dipping.