20.5 x 25.5cm brownie tin or baking tin greased and baselined
Heat the oven to 180C/350F/Gas 4. Break up the dark chocolate. Put into a heatproof bowl and melt gently.
Remove the bowl from the heat and leave to cool until needed. Put the butter and sugar into the bowl of a food mixer and beat until fluffy. Gradually beat in the eggs, beating well after each addition. Beat in the vanilla essence. Spoon the cooled melted chocolate onto the mixture then mix in thoroughly. Sift the flour and cocoa onto the mixture and gently stir in.
When completely combined spoon the mixture into the prepared tin and spread evenly. Bake in the heated oven for about 20 minutes until firm to the touch but still a bit fudgy – the chocolate will continue to cook slightly for a few minutes after coming out of the oven.
Remove the tin from the oven and set on a wire cooling rack. Leave to cool completely before cutting into pieces. Delicious eaten warm with ice-cream. Store in an airtight container and eat within 4 days.