Preheat your oven to 160 degrees and line the base and sides of a 20cm square baking tin with baking paper – this will help you to remove the Snickers Brownies once they are cooked.
Roughly chop the Snickers and set aside until needed.
Place the butter (which has been cut into 4 pieces, cocoa and caster sugar into your Thermomix bowl and cook for 3 minutes, 60 degrees, speed 2 to melt. If it's not quite melted, cook for a further 1 minute, 60 degrees, speed 2.
Add the vanilla extract, eggs and plain flour and mix for 10 seconds, speed 4 to combine.
Scrape down the sides of your Thermomix bowl and add the Snickers pieces you set aside earlier and mix for 6 seconds, speed 4 on REVERSE to combine.
Pour the brownie mixture into the prepared tin and use a spatula to gently spread it across the tin. Place the brownies into the oven to bake for 35 minutes.
Carefully remove the cooked brownies from the oven and allow them to cool in the tin before removing, cut into small pieces .
It’s important to let these Snickers Brownies cool completely in the tin as it will help their gooey centre to set.