Mung Beans and Sweet Potatoes Soup (Tong Shui)

Kindly excuse the colour of the above pic, due to my lack of skills instead of making it look real and better, I turned it looking a bit retro which reminded me of photos taken by my dad in the 70s. This tong shui is one of the simplest but big in taste! Just boil the mung (green) beans in some water until they're soften before adding the orange sweet potatoes. The sweet potatoes that I've