Start by cutting the pineapple in half lengthways. Remove the pineapple flesh from the skin and chop up the flesh into small cubes. Keep the pineapple skins whole as you will be serving the chicken in them. Next, start preparing the sweet and sour sauce. Put the sugar, minced garlic, ketchup, lime juice, rice wine or dry sherry and the soy sauce in saucepan and simmer gently for 5 minutes. Put the corn flour and water together in a glass and mix well. Add to the sweet and sour sauce, and mix to thicken. Take the sauce off the heat and put to one side. Next, you need to make the batter for chicken. Mix together the flours, baking powder, sugar and egg to make a paste. Add enough water to make a nice thick batter. Dip the chicken pieces into this batter, coating them all over. Immediately fry the battered chicken pieces in hot cooking oil, till golden brown, turning around constantly to get an even colour.It is important that you place the battered chicken pieces in the oil one at a time, otherwise they will stick together. Remove the cooked chicken pieces from the hot oil with a slotted spoon and put onto kitchen towel to absorb the excess oil. Finally, mix the chicken pieces with the pineapple chunks and the sweet and sour sauce. Serve the sweet and sour chicken in the prepared pineapple skins.