For the brownie batter, tip 250g unsalted butter and dark chocolate into a small pan over a low heat, and stir until melted and smooth. Remove from the heat and leave to cool. Heat the oven to 200C/180C fan/gas 6. Butter a 20 x 20cm square cake tin and line with baking parchment.

Crack the eggs into a large bowl, add the caster sugar and whisk until light and fluffy. Pour in the cooled chocolate mixture, and whisk again until everything is well combined. Sift in the flour and cocoa powder.

Mix the coffee granules with 2 tbsp hot water, then stir this into the brownie batter until the mixture is smooth and slightly runny. Pour into the tin and bake for 25 mins until set with a slight wobble. Leave to cool completely in the tin.

For the caramel cornflakes, tip the brown sugar and remaining 85g butter into a non-stick pan over a medium heat and cook, stirring, until the sugar has dissolved, about 5-7 mins. The mixture should be slightly fluffy and aerated on top. Add the double cream, stir and simmer for 5 mins over a low heat until smooth. Stir in 1 tsp salt.

Tip the cornflakes into a large heatproof bowl, pour over the salted caramel and mix with a silicone spatula until all the cornflakes are coated. Spoon this over the cooled brownie and carefully level the surface. Chill for at least 4 hrs or overnight until firm before cutting into squares.