1 For the pastry: In a bowl, mix the flour with cocoa, salt and sugar. Cut the butter into small pieces and with a pastry blender, cut the butter into the flour mixture until it resembles coarse crumbs. Add the egg and knead quickly into a pastry. Wrap in foil and refrigerate 30 minutes.
2 Preheat the oven to 180°C (approximately 350°F).
3 Roll out the dough on a lightly floured surface and fit it into a 28 cm (approximately 11-inch) tart pan pressing the dough into the bottom and up the sides of the pan. Line with parchment paper and fill the whole thing with the dried beans. Bake about 20 minutes. Reduce the oven temerpature to 150°C (approximately 300°F).
4 For the batter: Meanwhile, melt the chocolate and cool to room temperature. In the bowl of an electric mixer, beat the butter with the sugar and salt until foamy. Add the eggs, one at a time, beating well after each addition. Stir in the chocolate. Fold in the flour and chopped nuts.
5 Remove the parchment paper and beans from the tart pan. Pour the batter into the tart shell and place the pecan halves on top and press lightly into the batter. Bake the tart until a toothpick inserted in the center comes out clean, about 30 minutes. Let cool before cutting into wedges.