Line the base and sides of a 20cm square baking dish with baking paper.
Break the chocolate into squares and set aside until needed.
Place the sweetened condensed milk and butter into the Thermomix bowl and cook for 6 minutes, 100 degrees, speed 2.
Add the chocolate pieces and cook for 3 minutes 90 degrees, speed 3.
Add the Baileys and mix for 20 seconds, speed 3 to combine.
Working quickly, transfer the fudge into the prepared baking dish. Gently smooth the surface and place into the fridge for six hours to set.
Once the fudge has set, carefully slice into pieces. Store in the fridge until ready to enjoy.
Notes
I like to use a mixture of milk and dark chocolate, you can use all dark chocolate if you prefer.Once the chocolate has been added, work quickly to add the Baileys and transfer to the baking dish. The fudge will begin to set.Store fudge in an airtight container in the fridge. This recipe is not freezer friendly.