For the mini brownies

• Place the butter, sugar, cacao, salt and vanilla in the bowl where you're going to whip them up later.
• Put the bowl on a bain-marie without touching the surface of the water until everything is melted and mixed together.
• Remove the bowl from the bain-marie and wait 5min for it to cool down a bit. You should be able to touch the outside of the bowl without burning yourself.
• Beat using a stand or hand-held electric mixer and add the egg. Stop once it's completely incorporated.
• Add the flour and beat for 2min on high speed.
• Line a 20x20cm / 8x8in pan with baking paper and pour the batter inside. Take into a preheated oven at 180°C/350°F for 10min or until you can insert a toothpick at the centre and it comes out with a bit of dough (we don't want it to dry out completely).
• Let cool down completely, unmould and cut the mini brownies.