Cranberry-ripple dark chocolate brownies

1. For the ripple, heat the frozen cranberries in a pan until starting to defrost. Stir in the caster sugar and bring to the boil for about 3 minutes. Using a heatproof stick standing blender or liquidiser, purée  the cranberries until silky smooth.  Transfer to a bowl and set aside.

2. Preheat the oven to 190ºC, gas mark 5 and line a 23cm-square baking tin with parchment. In a large bowl, mix the cocoa powder, flour, baking powder and salt. In a separate bowl whisk together the butter, caster sugar, brown sugar, vanilla extract and eggs until well combined. Stir the wet mixture into the dry until just mixed. Fold in the chocolate chunks. Pour the batter into the baking tin and spread evenly.

3. Spoon the cranberry mixture onto the batter in 4 thick horizontal lines then, using the spoon at an angle, cut 4 vertical lines through to the bottom of the batter giving a rippling effect.

4. Bake the brownies for 30-40 minutes for gooey texture, or 35-45 minutes if you prefer them firmer. Remove from the oven and leave to cool before serving.