- First make the pastry. Whiz the butter and sugar in a food processor until just combined. Add the egg and whiz for 30 seconds. Add the flour and process for a few seconds until the dough just comes together (add 1 tablespoon of cold water if it seems too dry). Knead lightly on a floured surface, then shape into a flat disc. Wrap in cling film and chill for 30 minutes.
- Preheat the oven to 190°C/Gas 5. Lightly grease ten 8cm fluted loose-bottomed mini tart tins. Roll out the pastry as thinly as possible on a floured work surface and cut out 10 small discs using an 11cm fluted cutter. Line the tins with the pastry, allowing it to overhang the edges, then prick the base with a fork and rest for 20 minutes in the fridge. (They should be really firm and cold so that you can avoid having to blind bake them.)
- Bake the rested tart cases in the preheated oven for 12 minutes until golden. Use a sharp knife to trim off the excess pastry, then cool the cases in their tins on a wire rack.
- While the tarts are cooking, make the peanut brittle. Line a baking sheet with greaseproof paper or a lightly oiled sheet of foil. Put the sugar into a dry frying pan over a medium-high heat for 3–4 minutes and allow it to caramelise without stirring. Once the caramel begins to form, swirl it around the pan to ensure it colours evenly. After 2–3 minutes, when it’s beginning to turn light brown, add the peanuts and swirl to coat. Pour onto the prepared baking sheet, tilting it so that the peanut mixture spreads out thinly and evenly. It should harden almost immediately. Set aside for about 10 minutes to cool.
- Meanwhile, make the chocolate ganache. Put the chocolate, cream, butter and sugar into a heatproof bowl and place over a pan of gently boiling water for 7–8 minutes, stirring to combine once melted. (Taste and add a little sugar if you prefer a sweeter ganache.)
- Spoon the ganache mix into the cooled tart cases and top with broken shards of peanut brittle. Chill for 20 minutes, then serve.