Sweet potato cream

• 1) Heat egg yolk,sugar,butter in Bain Marie(water bath)
  2) Add the pre-soaked gelatin ( 1:5)
  3) Fold with 90% whipped DB whipping cream and the above and sweet potato filling
  

Lemon syrup

• Brush Lemon syrup to the sponge sheet and spread the sweet potato cream and sponge sheet again till 3 layers.
  Icing DB whipping cream at outside of the cake and sprinkle the cake crumb and place Pistachio kernel as the photo.
  

Decoration

• Squeeze whipped cream into a rose shape and decorate with pistachio kernel.