3 squares (1 ounce each) white baking chocolate, chopped
1 square (1 ounce) unsweetened chocolate, chopped
3/4 cup confectioners' sugar
2 tablespoons unsweetened cocoa powder
2 tablespoons confectioners' sugar
Line 2 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 by rounded teaspoonfuls onto prepared baking sheets. With your hands, quickly shape into balls. (Refrigerate to firm while working if necessary.) Place in freezer 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.