Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4. Grease and line a 20cm square cake tin.
2. Make the peanut butter batter. Whisk the peanut butter, sugar and egg together in a bowl until combined (it will be quite thick).
3. For the brownies, put the butter and caster sugar in a saucepan. Cook over a medium low heat, stirring, until melted together and smooth. Remove from the heat and stir in the chopped chocolate until it has melted. Pour into a mixing bowl and cool briefly, then mix in the eggs. one at a time. Add the flour and salt and stir until just combined. Fold in two-thirds of the blackberries, saving the rest for the topping.
4. Put the brownie batter in the tin, then dollop over big spoonfuls of the peanut butter batter. Use a knife or skewer to swirl the peanut and chocolate batters together. Gently push the remaining blackberries into the top of the batter.
5. Bake for 45-50 minutes; the brownies should be slightly squidgy in the centre. Let cool completely before cutting into squares.