Chocolate-cornflake cookies with mocha ganache

1.Preheat oven to 180°C and line 2 large oven trays with baking paper. Beat butter and sugar in an electric mixer until light and fluffy (4 minutes). Fold in sifted cocoa and flour, then chocolate and cornflakes until well combined. Roll heaped tablespoons of mixture into balls and press lightly to flatten. Place dough on prepared trays 4cm apart and bake until just firm to the touch, swapping trays halfway through cooking (16-18 minutes). Cool completely on trays.

2.For mocha ganache, combine ingredients in a heatproof bowl over a saucepan of simmering water (don’t let bowl touch water) and stir until melted and smooth. Roll edges of biscuit in ganache to coat, then place on oven trays lined with baking paper and scatter with walnuts. Set aside until ganache sets (20 minutes).