Preheat oven to 160 degrees celsius (fan forced) and line two flat baking trays with baking paper. Set aside.
Place the caster sugar and butter into the Thermomix bowl. Add the butterfly and mix on Speed 4, 20 seconds. Scrape down the sides and repeat once more (or until pale and fluffy).
Add the egg and mix for a further 10 seconds, Speed 4.
Remove the butterfly, add the Milo and self raising flour and mix on Interval (knead function) for 1 minute (or until completely combined).
Chill the dough in the fridge for a minimum of 30 minutes to help the biscuits keep their shape when cooked (optional step).
Roll the mixture into tablespoon-sized balls and place onto the prepared trays (leaving a gap to allow for spreading).
Press the balls down slightly. Bake for 15 minutes.
Allow to cool on the trays for 10 minutes before transferring to a wire rack to cool completely.
Optional: When the biscuits are completely cooled, decorate with a small amount of melted white chocolate and sprinkles.