Melt 50g dark chocolate in a heatproof bowl set over a pan of barely simmering water. Cool for 5 minutes.
Whisk together the butter and sugar until pale and fluffy, then beat in the egg and melted chocolate. Stir in the flour, bicarbonate of soda, 100g mincemeat, cocoa powder, ½ tsp sea salt, 100g chocolate and the pecans. Chill the dough in the fridge for an hour until firm.
Preheat the oven to 180°C, gas mark 4.
Divide the dough into 14. Roll one piece into a ball and flatten in the palm of your hand to a 7cm circle. Fill with 1 tsp mincemeat, fold the dough over and roll back into a ball. Repeat with the rest of the dough and filling and arrange on the tray.
Bake for 10 minutes. While the cookies are in the oven, melt the remaining chocolate as before.
Remove the cookies from the oven and leave to cool completely on the tray. Drizzle with the melted chocolate and serve.