Nutrition: per serving (8)
Heat the oven to 180C/160C fan/gas 4. Butter and line a 25cm rectangular tin with baking paper. Put the butter and both sugars in a large bowl, and beat together using an electric whisk for 4-5 mins or until light and fluffy.
Tip the eggs into a large jug, then whisk in the soured cream and oil. Pour into the beaten butter a little at a time, whisking between each addition. Sift over the dry ingredients and fold to combine. Pour into the tin and bake for 20-25 mins or until a skewer comes out clean. Leave to cool in the tin for 5 mins, then remove to a wire rack.
For the icing, put the butter in the bowl of a stand mixer or large bowl and whisk for 4-5 mins or until pale. Add the peanut butter and whisk to combine, before pouring in the vanilla and half the icing sugar. Whisk to combine then, once smooth, add the remaining icing sugar. Add a splash of milk to the icing if it is too thick.
Smooth the icing on top of the cake, sprinkle with peanuts and chocolate shavings, and serve in chunky slices with a cup of tea.
