To ensure a smooth cheesecake, bring all ingredients to room temperature before starting.
Grease and line the base and sides of a 23cm spring-form pan with baking paper and set aside.
Melt butter in the Thermomix bowl for 2 minutes, 100 degrees, Speed 1.
Add 300g of the Tim Tam biscuits and crush on Speed 10 for 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.
Roughly chop the remaining 100g Tim Tam biscuits and set aside.
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 a few minutes). Set the cream aside in a separate bowl.
Pour ¼ cup of hot water into a cup, sprinkle over the gelatine and stir with a fork until dissolved. Set aside and allow to cool.
Beat the cream cheese, vanilla bean paste and caster sugar in a clean and dry Thermomix bowl for 30 seconds, Speed 5. Scrape down the sides with a spatula and repeat until smooth and creamy.
Add the cooled, dissolved gelatine to the mix and mix for 30 seconds, Speed 5. Divide the mixture evenly between two bowls.
Place the milk chocolate into the Thermomix bowl. Grate for 5 seconds, Speed 8. Scrape dow the sides of the bowl. Melt for 3 minutes, 50 degrees, Speed 2. Set aside in a bowl.
Fold the melted milk chocolate, half of the whipped cream and half of the chopped Tim Tams through one portion of the cream cheese mixture.
Spoon the milk chocolate mixture into the prepared tin. Spread out evenly with a spoon. Place into the fridge for 15 minutes.
Place the white chocolate into the Thermomix bowl. Grate for 5 seconds, Speed 8. Scrape dow the sides of the bowl. Melt for 3 minutes, 50 degrees, Speed 2. Set aside in a bowl.
Fold the melted white chocolate, the remaining whipped cream and chopped Tim Tams through the second portion of the cream cheese mixture. Carefully spoon the mixture over the milk chocolate layer and spread out evenly with a spoon.
Place the cheesecake into the fridge to set for a minimum of 6 hours. TIP: For best results, leave in the fridge overnight.
Decorate with extra chopped Tim Tams before serving, optional.