In a large bowl, stir together flour, granulated sugar, cocoa powder, baking powder, and salt. Using a pastry blender, cut in the butter until mixture resembles coarse crumbs. Make a well in the center of dry ingredients; set aside.
In a small bowl, stir together egg, 1/2 cup whipping cream, and vanilla. Add egg mixture to flour mixture. Add chocolate pieces and, if you like, the pecans. Using a fork, stir just until moistened.
Turn dough out onto a lightly floured surface. Gently knead dough by folding and gently pressing dough for 10 to 12 strokes or until dough is nearly smooth. (Handle dough as little as possible to keep it light.) Divide dough in half. Lightly roll or pat each dough half into a 4-1/2-inch circle, about 1-inch thick. Cut each round into 6 wedges. Place wedges 1 inch apart on a parchment-lined baking sheet or an ungreased baking sheet. If you like, brush scones with additional whipping cream and sprinkle with coarse sugar.
Bake in a 400 degree F oven for 12 to 14 minutes or until bottoms are lightly browned. Remove scones from baking sheet. Cool on a wire rack for 5 minutes. Serve warm. Makes 12 scones.