Insert the butterfly whisk into the Thermomix bowl. Add the cream and whip for 2-3 mins/speed 3 with the measuring cap off. Observe the cream carefully through the lid after 30 seconds to avoid over-whipping. If you're unsure about the thickness, stop, open the lid, and mix again for another 3+ second increments. Whip the cream until stiff peaks form.
Once the cream is whipped, add the sweetened condensed milk, peppermint extract and cocoa powder and blend for 10 sec/speed 3 with the measuring cup on. Scrape down the sides of the bowl with a spatula, then mix again for 10 sec/speed 3. Stir in any loose bits of cream into the mixture with a spatula.
Transfer the mixture to a freezer-proof container and freeze for at least 6 hours.
Before serving, let the ice cream sit on the benchtop for a few minutes to be soft enough to scoop.
Notes
Storage: Store the ice cream in an airtight, freezer-safe container with baking paper or cling film pressed onto the surface to prevent ice crystals. When ready to serve, let it soften at room temperature for a few minutes. Consume within two weeks.