Directions

1. First, make the pastry. Tip the flour, cocoa, butter and a pinch of salt into a food processor and blitz until the mixture resembles fine breadcrumbs. Add the egg yolk, icing sugar and 2 tbsp cold water and blitz again until just starting to clump together. Tip onto your work surface (don't worry about washing the bowl), knead briefly into a smooth ball of dough, then flatten into a thick disc shape, wrap in cling film and chill for 30 mins.
2. Add the remaining ingredients - except for the jam and the peanuts to serve - to the food processor and blitz until smooth and creamy. Heat oven to 180C/160C fan/gas 4.
3. Remove the pastry from the fridge and roll out to the thickness of a PS1 coin. Lift the pastry into a 22cm fluted tart tin and press it into the corners, taking care not to rip it. Trim the excess pastry with scissors, leaving an overhang of about 1cm. Line with baking parchment and baking beans, and bake for 15 mins.
4. Remove the parchment and beans and return to the oven for 5 mins more, until it looks biscuity. Remove from the oven and use a small serrated knife to trim the pastry to the height of the tin. Discard (or nibble on) the off-cuts.
5. Spoon the jam onto the base of the tart and spread to the edges. Top with the peanut mixture, spreading to the edges to cover the jam. Bake for 45 mins until the sponge is cooked and a skewer inserted into the centre comes out clean. Cool in the tin for 15 mins, then transfer to a wire rack to cool completely.
6. Mash the remaining icing sugar and jam together to make a smooth icing and drizzle on top. Roughly chop the remaining peanuts and scatter over. Leftovers will keep in an airtight container for 3 days.