Place truffle into the Thermomix bowl and mill 5 sec/speed 8. Scrape down sides of bowl.
Add butter and salt and blend, 10 sec/speed 6 or until well combined. You can insert the Butterfly and whip 20 sec/speed 4 but the colour of the butter will become grey. The flavour is more throughout the butter though.
Turn out onto a piece of baking paper and scrape together into a roll. Wrap tightly and keep frozen until use. Slice off in rounds to use on anything you need!