Grease and line an 18X28cm baking tin with baking paper and set aside.
Place the butter into the Thermomix bowl and melt on 100 degrees, Speed 2, 3 minutes. Add the Oreo cookies and crush on Speed 6, 10 seconds.
Press into the prepared tin and smooth down with a spoon. Place into the fridge.
Place the cream cheese, caster sugar and vanilla extract into the Thermomix bowl and mix on Speed 5, 10 seconds. Scrape down the sides and repeat for a further 10 seconds or until smooth and creamy.
Add the cream, dissolved gelatine and cooled melted chocolate and mix on Speed 6, 10 seconds.
Add a few of the mini Oreos and mix on Reverse, Speed 5, 10 seconds. Spread the mixture over the top of the prepared base.
Top with the mini Oreos and place into the fridge for 3-4 hours or until set.
Cut into pieces and store in an airtight container in the fridge for up to 1 week.