Preheat oven to 180 degrees celsius (fan-forced).
Grease and line 2 baking trays and set aside.
Place room temperature butter and caster sugar into the Thermomix bowl. Cream 45 seconds, Speed 5 (scrape down the sides after 20 seconds).
Add the condensed milk and mix for a further 20 seconds, Speed 5.
Add the self-raising flour and Milo and mix for 20 seconds, Speed 6. Scrape down the sides of the bowl and repeat for a further 5-10 seconds or until completely combined.
Roll into teaspoon-sized balls and place onto the prepared baking trays. Press down lightly with a fork.
Bake for 10 minutes. Allow to cool for 10 minutes on the baking trays before transferring to a wire rack to cool completely.