In a large mixer bowl beat butter or margarine and sugar with electric mixer on medium speed till fluffy. Add bourbon; beat well. Gradually add flour and cocoa powder, beating till well mixed. Stir in chocolate pieces. Chill 2 hours or till firm enough to handle. Shape dough into 1-inch balls. Roll in egg white, then in nuts. Place on a lightly greased baking sheet. Bake in a 350 degree oven about 12 minutes or till edges are firm. (The center will still be soft.) Cool on baking sheet 1 minute. Cool on wire racks. Makes about 30. Per cookie: 104 cal, 1 g pro., 9 g carbo, 7 g fat, 9 mg choL 40 mg sodium cook 001