Martha's mocha swirl blondies

Preheat the oven to 180ºC, gas mark 4. Grease and line a 20x20cm square tin with baking parchment. In a large saucepan, heat the butter, light brown sugar and caster sugar together until the mixture has completely melted. Remove from the heat and allow to cool for 5 minutes, then add the chunks of white chocolate. Stir until melted, then allow the mixture to cool to room temperature – if you don’t allow it to cool, the eggs will scramble when you add them.

Beat the eggs into the cooled mixture using a wooden spoon. Sieve over the flour and baking powder and mix until well combined. Dissolve 2 tsp coffee powder in 1 tsp of boiling water, then stir this paste into the batter.

Spoon three-quarters of the mixture into the prepared tin and use a spatula to spread it out evenly. Add the cocoa powder to the remaining mixture and mix well. Use a teaspoon to dollop this chocolate mixture randomly over the coffee mixture, then use a skewer to swirl the mixtures together. Sprinkle over the cacao nibs.

Bake the blondies for 25-30 minutes, or until risen with a slight wobble in the centre. Leave in the tin to cool completely, preferably overnight (if you can resist!) for them to become fudgy and dense before slicing. These blondies will keep for 1-2 weeks in an airtight container.