Preheat oven to 170°C and line a 20cm square baking tin with baking paper with some overhang so you can remove easily once cooked.
Place the butter, sugar and cocoa powder into the Thermomix bowl and heat for 3 mins/70/speed 2.
Add vanilla essence and eggs and mix for 35 secs/speed 4. Scrape down sides.
Add flour and salt and mix for 4 sec/speed 5. Scrape down the sides of bowl tand mix again for 3 sec/speed 5.
Pour mixture into prepared tin. Cook for 25-30 mins. Check consistency with toothpick at 20 minutes. Remember to undercook slightly to avoid a cakey texture as the brownie will continue to cook whilst cooling and resting.
Leave to cool completely in the tin before cutting up into squares.
