This is a traditional favorite in Hong Kong, found in most dessert houses and revered for its heartwarming and revitalizing properties. It can just be as easily prepared at home, and is sure to warm even the coolest of days (though it's popular all year-round). Yellow, red, and purple sweet potatoes are commonly found in the market, though yellow ones are ideal given its richer flavor. The amount of ginger may be adjusted according to level of tanginess desired. Red dates are natural sweeteners that add more flavor (optional). Raw slab sugar is commonly used in Southeastern Chinese desserts, and can be readily found in Asian groceries. The slab sugar is ideal for this recipe as it not only enhances the taste but also adds a nice golden color. A light, non-creamy, easy and healthy dessert that works great for any time of the day... and especially when you are down with a cold.