This is a different way to cook sweet potatoes. It's a refreshing dessert. A perfect finish to an Asian meal, especially after heavy stuff like curry. It's served cold, so it's great for summer too. And you can use up those leftover cooked sweet potatoes. Agar-agar powder can be found in Asian groceries store/market. I prefer making jelly-type desserts using agar rather than gelatin because of the IMHO, better texture. To make an impressive dessert, you can set the jelly in a pretty mold or cut it into cute little shapes using cookie cutters (I usually use metal ones). Adapted from Amy Beh's recipe. Cooking time = chilling time (approximation).