Chè Khoai Lang Đậu Xanh-Sweet Potato and Mung Bean Soup

Patti LaBelle's sweet potato pie is flying out of Wal Mart shelves.   Before I learn how to make that famous pie, I will share with you a humble Vietnamese dessert from Sweet Potato.  We usually use the orange-color flesh for this soup.  Fresh coconut milk will give the soup the best flavor as always but canned one is what available for most of us here.  Pandan leaves can be found in in frozen section if fresh is not available.

Make 4 cups

1/4 cup skinless mung bean
2 cups water, divided
1 sweet orange flesh potato about 11-12 ounces
1/2 cup canned or fresh coconut milk
2 Tablespoons pearl balls/tapioca pearls,small size
1/2 cup sugar, divided
1/2 teaspoon salt
1 teaspoon pure vanilla extract or few pandan leave (fresh or frozen)

1. Soak skinless mung bean in hot water.  Set aside for 20 minutes.  
2. Peel and cut sweet potato into 1/2 inch cubes.  Soak them in cold water.
3. Rub soaked mung bean slightly, rinse well to get rid most of yellow dye.  In a medium saucepan, add bean, pandan leaves if use and 1 cup cold water.  Bring it to a boil.  Keep an eye close when it starts boiling, reduce the heat down to simmer gently, covered on low/med. low heat until very tender about 20 minutes.
4. Add potato, salt, and 1 cup water, bring it to a boil, add pearl balls. Then adjust the heat to simmer, covered, until sweet potato tender about 5 minutes.
5. Stir in 2/3 of sugar, coconut milk, vanilla (if do not use pandan leave).  Bring it back to a boil.  Taste and add more sugar if you want sweeter taste.  Then remove from heat, remove and discard the pandan leaves if use.  The soup will thicken lightly when cooling.  Serve warm or room temperature.