175 g (6 oz) unsalted butter, plus extra for greasing
200 g (7 oz) plain dark chocolate, broken into small pieces
75 g (3 oz) crunchy peanut butter
125 g (4 oz) smooth peanut butter
3 large eggs
175 g (6 oz) caster sugar
1/4 teaspoon salt
50 g (2 oz) self-raising flour
Grease a 30 x 20 cm (12 x 8 inch) brownie tin and line with nonstick baking paper (see page 9). Place the butter, chocolate and crunchy peanut butter in a small saucepan over a low heat and warm until just melted. In a separate saucepan, gently warm through the smooth peanut butter.
Meanwhile, place the eggs, sugar and salt in a large bowl and whisk until combined. Using a rubber spatula, stir in the melted chocolate mixture and flour.
Scrape the mixture into the prepared tin. Drizzle over the smooth peanut butter in 3–4 straight lines, then ‘drag’ through the peanut butter with the tip of a sharp knife to create a marbled effect.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 18–20 minutes until just firm to the touch, but with a slightly fudgy texture. Leave to cool in the tin for 1–2 minutes, then lift on to a board using the lining paper and cut into 12–16 squares. Serve warm or cold.