Passion Fruit Yo Yo Biscuits

A playful Asian take on an Australian classic, these sandwiched biscuits are sometimes called melting moments. They are made with custard powder instead of the standard cornflour, which adds a creamy vanilla flavour, though either ingredient works fine (custard powder is annatto-flavoured cornflour). The buttercream can be flavoured with citrus or berries, so feel free to swap flavours.