1. Peel yam, cut into pieces and steam until soft.
2. While it is still hot, transfer yam into bowl and add wheat starch, sugar, five spice powder, cooking oil and salt. Mash the yam and knead it until it forms a pliable dough - add additional wheat starch if it is too sticky; if it is too dry, increase amount of cooking oil.
3. Place the yam paste in a ziplock bag and seal the opening. Compress until it forms a thick piece and place in freezer for about 20-30 mins.
4. Once the yam paste is slightly firm (but still pliable), open the ziplock bag. Cut into 3 equal parts of about 5cm wide each.
5. Take the ends of the cut strips and connect them together. Pop it back into the freezer until firm for deep frying. Just remember to defrost the ring slightly before deep frying.
6. In a bowl, mix sweet and sour sauce ingredients until well blended.