Grease and line the base and sides of a 20cm spring-form pan with baking paper and set aside.
Melt butter in the Thermomix bowl for 2 minutes, 100 degrees, Speed 1. Add the chocolate biscuits and crush on Speed 10, 10 seconds. Scrape down the sides of the bowl and repeat until well combined.
Press the mixture firmly into the base of the pan and place into the fridge.
Whip the cream in a clean, dry Thermomix bowl on Speed 3.5 until lightly whipped (the time it takes will depend on the freshness of the cream – it can be anywhere between 10 seconds and 2 minutes!!). Set the cream aside in a separate bowl.
Sprinkle the gelatine powder over ⅓ cup cool water in a small bowl and allow to sit for a minute or two. Stir. Place the small bowl into a larger bowl filled with boiling water (do not allow the boiling water into the gelatine bowl) and stir until completely dissolved. Set aside.
Beat the cream cheese and caster sugar in a clean and dry Thermomix bowl on Speed 5, 30 seconds. Scrape down the sides with a spatula and repeat until smooth and creamy.
Add the cooled, dissolved gelatine to the mix and mix on Speed 5, 30 seconds.
Fold the whipped cream, Maltesers and chopped Crunchie bars through the cream cheese mixture with the spatula.
Spoon the mixture into the prepared tin. Spread out evenly with a spoon.
Place the cheesecake into the fridge to set for a minimum of 6 hours (for best results, leave in the fridge overnight before cutting).
Before serving, decorate with extra Maltesers and Crunchie bars.