In a stainless steel bowl, over a saucepan of simmering water, melt the chocolate and butter. Remove from heat and set aside. In the bowl of your electric mixer (or with a hand mixer), beat the eggs and sugar until thick, pale, and fluffy. (When you slowly raise the beaters the batter will fall back into the bowl in slow ribbons.) At this point beat in the vanilla extract and then stir in the melted chocolate mixture. In a separate bowl whisk together the flour, salt, and baking powder. Add dry ingredients to the chocolate mixture, stirring just until incorporated. Cover with plastic wrap and refrigerate until firm enough to shape into balls (3-4 hours or overnight). Preheat oven to 325 degrees F (170 degrees C) and place rack in center of oven. Line two baking sheets with parchment paper, and set aside. Place the confectioners sugar in a shallow bowl. With lightly greased hands, roll a small amount of chilled dough to form a 1 inch (2.54 cm...