PREPARATION:

1. Preheat oven to 400°F. Grease cookie sheets well; set aside.
2. Beat butter and sugar in small bowl with electric mixer at medium speed until light and fluffy. Beat in egg whites, 1 at a time. Beat in vanilla. Add flour; beat at low speed just until blended. Gently fold in grated chocolate with rubber spatula.
3. Drop teaspoonfuls of batter 4 inches apart onto prepared cookie sheets. Spread dough into 2-inch rounds with small spatula. Make only 3 to 4 rounds per sheet.
4. Bake 1 sheet at a time 4 to 5 minutes until edges are barely golden. Do not overbake.
5. Remove from oven and quickly loosen edge of 1 cookie from baking sheet with thin spatula. Quickly roll cookie around clean handle of wooden spoon overlapping edges to form cigar shape. Repeat with remaining cookies. (If cookies become too firm to shape, return to oven for a few seconds to soften.) Slide cookie off handle to wire rack; cool completely.
6. Store tightly covered at room temperature or freeze up to 3 months.