Line the tray: line a baking tray with baking paper and set aside.
Crush the biscuits: add plain vanilla biscuits to food processor and blitz for 5 seconds to form a rough crumb. Transfer into small bowl and set aside (decoration).
Crush the Maltesers: add Maltesers to food processor and blitz for 10 to 15 seconds till roughly crushed.
Combine: transfer the crushed Maltesers into a medium sized mixing bowl, add the sweetened condensed milk and stir to combine.
Roll into balls: use a mini cookie scoop to portion the wet truffle mixture and place onto lined baking tray. Then work individually to pick up each portion and roll it into a ball.
Chill the truffles: place the truffles into the fridge for at least 30 mins.
Melt the chocolate: add the chocolate to a heatproof jug and use the microwave to melt it for 1-2 mins. Remove and stir after 1 min, then 2 mins.
Coat the truffles: remove truffles from the fridge, using a fork and working one by one, place the truffles onto the fork and dip into the melted chocolate. Pull the fork up and hold it above the jug. Gently shake to allow excess chocolate to drip off. Use a skewer at the base of the truffle to push it off the fork onto the tray.
Decorate the truffles: pour remaining chocolate into a zip lock bag and use scissors to snip a tiny hole on one side of the bag. Drizzle the chocolate back and forth over the truffles to decorate. Sprinkle biscuit crumbs on top of the melted chocolate (optional).
Serve: place in the fridge until ready to serve.