Preheat the oven to 160°C/320°F (140°C fan) and line a 20cm square baking tin with baking paper.
Place the butter, sugar and cocoa powder into the Thermomix bowl and heat for 3 min/50℃/speed 2.5.
Set the Thermomix to 1 min/speed 3 and add the eggsone at a time through the hole in the lid, followed by the vanilla extract. Keep the Thermomix running until the end of the minute.
Add the flourand mix for 3 sec/speed 5. Scrape down the bowl, then mix again for 3 sec/speed 5 until thoroughly combined.
Pour the batter into the prepared tin and bake in the oven for 30-35 minutes until the centre is set.
Leave to cool completely in the tin before cutting up into 16 squares.
Notes
Storage: If any brownies are left over, store them in an airtight container in a cool place for a few days.To freeze: Separate each brownie with baking paper, so they don’t stick together and freeze in an airtight container for up to three months.