Makes 12

100g butter, plus extra for greasing
180g plain chocolate, chopped
80g plain flour
½ tsp baking powder
150g caster sugar
3 large eggs
2 tsp vanilla extract

For the filling:
40g butter, melted
60g icing sugar
200g peanut butter
Pinch of salt
½ tsp vanilla extract

1. Preheat the oven to 150˚C/130˚C fan/gas mark 2. Butter a 20cm square baking tin and line with parchment paper.
2. Melt the butter and chocolate in a bowl set over a saucepan of simmering water. Remove from the heat and stir until smooth.
3. Whisk together the flour and baking powder in a separate bowl.
4. Whisk the sugar into the chocolate mixture, then gradually whisk in the eggs until smooth.
5. Stir in the vanilla, then stir in the flour until incorporated.
6. Stir together all of the filling ingredients in a separate bowl.
7. Spread the batter into the pan. Add dollops of the peanut butter filling all over, then use a knife to swirl it through.
8. Bake for 40-45 minutes until a skewer inserted into the centre comes out clean. Leave to cool before slicing.

Per serving: 364kcals, 22.6g fat (10.1g saturated), 36.6g carbs, 29.1g sugars, 7g protein, 2.1g fibre, 0.212g sodium