Line a 20cm square cake tin with baking paper, making sure to leave some paper hanging over the edges.
Break the white chocolate into pieces and place in the Thermomix bowl.
Add the condensed milk and cook for 10 minutes, 100 degrees on speed 3.
Add the Oreo Cookies and mix for 20 seconds on reverse, speed 1.
Working quickly, pour the fudge into the prepared pan and place in the fridge for 4 hours (preferably overnight) to set.
Remove fudge from the fridge and cut into small pieces.