Spread coconut in a shallow layer in a 15" x 10" jellyroll pan. Bake at 350° for 13 to 14 minutes or until toasted and dry, stirring once. Cool and transfer coconut to a small zip-top plastic bag. Finely crush coconut, and set aside.
Beat butter at medium speed of an electric mixer until creamy. Gradually add sugar, beating until light and fluffy. Add chocolate; beat well. Add egg and vanilla; beat well.
Combine flour, baking powder, soda, and salt; add to butter mixture, beating until blended. Stir in half of coconut.
Divide dough into thirds; place on 3 large sheets of plastic wrap. Roll each portion lengthwise in plastic wrap, and shape into a 10" log. Cover with plastic wrap, and chill logs 30 minutes. Reroll logs, if necessary.
Combine remaining coconut and pecans. Unwrap logs; brush lightly with milk, and roll in pecan-coconut mixture, pressing firmly to make coating adhere. Wrap in plastic wrap and freeze logs at least 8 hours.
Cut into 1/4" slices, using a sharp knife. Place 1" apart on ungreased cookie sheets. Bake at 375° for 8 to 9 minutes or until edges are browned. Cool 1 minute on cookie sheets; remove to wire racks, and cool completely.