Line two baking sheets with waxed paper. Heat cognac in a small saucepan just to simmering. Remove from heat. Add cream. Bring to simmering. Place all the chocolate and 3/4 cup confectioners’ sugar in a food processor and whirl 1 to 2 minutes or until finely chopped. With machine running, add cream mixture in a steady stream. Process until smooth. Scrape into a medium-size bowl. Refrigerate just until thick enough to hold shape (about 1 hour). Drop rounded teaspoonfuls onto prepared baking sheets. With your hands, quickly shape into balls. (Refrigerate to firm while working if necessary.) Place in a freezer for 30 minutes. Prepare coating: Sift cocoa powder and confectioners’ sugar into a small bowl. Add truffles, 3 at a time; toss to coat. Refrigerate in airtight containers up to 1 month. Serve at room temperature.