Ingredients

Step by step

1. Preheat the oven to 170°C, fan 150°C, gas 31⁄2. Grease and line a 900g loaf tin (measuring 9cm x 20cm on the base). Roughly chop half the chocolate, place this in a heatproof bowl and set over a pan of barely simmering water to melt. Set aside to cool slightly. Finely chop the remaining chocolate. Place the unsalted peanuts in a small food processor and whiz until finely ground.
2. Place the butter, sugar and peanut butter in a mixing bowl and beat until smooth and well combined. Beat in the eggs and soured cream then fold in the ground peanuts, flour and baking powder until well combined. Spoon half the mixture into another bowl.
3. Stir the melted chocolate, chopped chocolate and cocoa powder into one of the mixtures. Dollop alternate spoonfuls of each mixture into the tin, then run a flat-bladed knife through the mixture a couple of times to swirl it together.
4. Bake for 1 hour 10 minutes (covering with foil for the last 10 minutes if it begins to brown too much) until a skewer comes out clean. Cool the cake in the tin for 10 minutes, then turn out onto a wire rack and peel off the baking paper.
5. To make the topping, place the sugar and 3 tablespoons of water in a small saucepan. Heat gently, swirling the pan until the sugar dissolves. Do not stir it otherwise the sugar will crystallise. Bring to the boil and boil for 6-8 minutes until the sugar turns a rich caramel colour, again swirling the pan rather than stirring, until evenly coloured. Slowly whisk in the soured cream until smooth. The mixture needs to be a thick pouring consistency, so cook a little longer if necessary, stirring, until it reduces a little. Stir in the peanuts and pour over the loaf. Allow to cool and set.
   Tip

   Make it gluten free
   Use gluten-free flour and baking powder, adding 1⁄2 tsp xanthan gum with the dry ingredients