Place the softened butter, brown sugar and caster sugar into your Thermomix bowl and mix for 30 seconds, speed 3. Scrape down the sides of the bowl and mix for a further 20 seconds, speed 3 or until pale and creamy.
Add the milk, vanilla extract and egg and mix for 10 seconds, speed 3.
Scrape down the sides of the bowl and add the flour, cinnamon, bicarbonate of soda, baking powder and mix for 10 seconds, speed 4.
Scrape down the sides of the bowl and add the rolled oats and raisins and mix for 20 seconds, speed 3, reverse to combine. Place the mixture into the fridge to chill for 30 minutes.
Preheat your oven to 180 degrees celsius and line two trays with baking paper.
Use a tablespoon to scoop up the biscuit mixture and roll it into balls before placing onto the prepared baking trays. Gently flatten the top of the biscuit before repeating until all the mixture has been used.
Place the baking trays into your oven and cook for 12 - 15 minutes or until the biscuits begin to turn golden on top. Carefully remove from the oven and let the biscuits cool for 5 minutes on the trays before transferring them to a wire rack to cool completely.