Plantain Empanadas

To make custard, whisk milk with 2 tbsp cornflour, egg, vanilla and sugar in a saucepan until well combined. Add cinnamon and bring to the boil, stirring continuously with a wooden spoon. Reduce heat to low–medium and cook, stirring, for 6 minutes or until the mixture is thick enough to coat the back of the spoon. Strain into a bowl, cover surface with plastic wrap and cool. Refrigerate until needed. The custard will keep in an airtight container in the fridge for up to 3 days.
Meanwhile, cut hard end from plantains and discard, then cut into 2 cm slices. Place in a saucepan, cover with water, then bring to the boil. Cook for 6 minutes or until pierced easily with a fork and just turning from pale to deep yellow. Drain, place in a bowl and mash. Add remaining 2 tsp cornflour and stir to combine.
When just cool enough to handle, divide plantain mixture into 16 balls (about 2 tbsp each). Lay a 20 cm sheet of baking paper on a work surface and place 1 ball in the centre, then cover with another sheet of baking paper. Using a plate, press down on mixture to form an 11 cm round. Remove top sheet of paper, then spoon 2 tsp custard into centre of the round. Carefully fold paper in half by lifting both sides to meet in the middle. Working from outside the paper, gently press edges of mixture together to seal and enclose filling. If mixture cracks, gently run your fingers over paper to seal cracks. Unfold paper and transfer empanada to a tray. Repeat with remaining plantain mixture and custard. Cook immediately or cover with plastic wrap and leave at room temperature for up to 1½ hours.
Fill a deep-fryer or large saucepan one-third full with oil, then heat over medium heat to 170°C (or until a cube of bread dropped into oil turns golden in 15 seconds). Working in batches, gently drop empanadas into oil and fry, turning halfway, for 4 minutes or until golden brown. Remove with a slotted spoon and drain on paper towel. Dust empanadas with icing sugar to serve.