Method

• 1.
  To make the filling, place the mung beans in a medium heatproof bowl. Cover with 2cm boiling water. Set aside to cool. Cover with plastic wrap and chill overnight.
• 2.
  For the shell, steam potatoes for 15-20 minutes (do not boil, or potatoes will be too wet), until a fork can be inserted with no resistance. Transfer potato to a large bowl. Mash with a fork until smooth. Add sugar and 1/4 tsp fine salt, and mix until combined. Sift flours and baking powder over potato mixture. Pour over 1/2 cup (125ml) boiling water and the oil and stir, then add 1/4 cup (60ml) room-temperature water bit by bit, until it forms a smooth dough. Check the moistness of the dough – if there’s a lot of dry flour that can’t be incorporated, add more room-temperature water, 1 tsp at a time, until there is no more dry flour left; if it’s too wet, dust with plain flour as needed (a dryer dough is better for frying). Use your hands to gently knead the dough. Cover with plastic wrap and rest for 30 minutes.
• 3.
  Drain soaked mung beans and then steam over medium heat for 30 minutes until completely soft. Transfer warm mung beans to a food processor with the sugar, vanilla, 1/4 cup (60ml) coconut cream and 1/4 tsp fine salt, and whiz to a paste. Transfer to a small saucepan. Add the remaining coconut cream and cook, stirring constantly, over medium-low heat, for 4 minutes, to remove moisture from filling. Transfer to a mixing bowl. Set aside to cool. Roll the filling into 30 x 10g balls, placing them as you go on a large baking tray lined with baking paper.
• 4.
  Place the sesame seeds in a fine sieve and rinse under running water until well soaked. Drain well, then transfer to a plate, spreading out in an even layer and patting dry with paper towel if too wet (they should be hydrated, but not puddled with water).
• 5.
  With floured hands, measure out 15g of the shell dough and spread it out to 5cm between your fingers. Place a ball of filling in the centre and cover it with shell dough, making sure it’s fully enclosed (the shell is very forgiving; if it tears, simply press it together again to cover the filling). Using the palms of your hands, finish the ball by quickly rolling it into a smooth uniform sphere, then roll the ball in sesame seeds to cover thoroughly. Return to the tray and repeat to make 30 balls (see note).
• 6.
  Heat 7cm of extra oil in a large saucepan until 160°C (a cube of bread will turn golden in 3 minutes when the oil is hot enough). Deep-fry 6-7 balls at a time for 8-9 minutes, until golden brown and crisp. Make sure not to crowd the pot, and use a wire skimmer to keep the balls submerged and moving as they expand and float to the top, to ensure a crispy shell. Check the oil temperature between each batch. Transfer the fried balls to a plate lined with paper towel to drain and cool for 5-10 minutes before serving warm or at room temperature.