Cut the Chinese yam and purple sweet potato into slices and steam them separately until fully cooked and soft, which should take about 15 minutes.
Strain the cooked yam and sweet potato and let them cool for 10 minutes.
Mash the purple sweet potato and form it into small 1cm balls.
In a new bowl, mix the steamed Chinese yam, formula milk, plain flour, and Baby Angel's Homemade baby superfood powder until the mixture is smooth.
Sprinkle some plain flour on a chopping board to prevent the mixture from sticking to your hands.
Take a small amount of the mixture and form it into a long shape, then cut it into 2cm pieces.Press the mixture to flatten it and place a purple sweet potato ball in the center.
Wrap the mixture around the sweet potato ball and flatten it slightly. Repeat with the remaining mixture and sweet potato balls to make around 12 sandwich cakes.
Open 3 lines on each sandwich cake and sprinkle Baby Angel's homemade seaweed sesame powder on top for extra flavor.
Heat a non-stick pan, like the Korea Didinika pan, and add some oil.
Gently place the sandwich cakes in the pan and fry for about 5 minutes on each side until golden brown.