1. In a large bowl, beat 1/2 cup butter or margarine until creamy.

2. Add the sugar, and beat until mixed well.

3. Beat in egg and mint extract.

4. Sift flour, cocoa, and salt together into a small bowl.

5. Add flour mixture by halves into creamed mixture, beating well after each addition.

6. Divide dough in half. On lightly floured surface roll dough into two 1 1/2 inch diameter cylinders.

7. Wrap each cylinder in waxed paper, and refrigerate 5 hours.

8. Freeze each cylinder for at least 30 minutes. Cylinders may remain frozen to make only half a batch at a time.

9. Preheat oven to 350 degrees F (175 degrees C).

10. Remove one cylinder at a time, and slice 1/4 inch thick pieces with very sharp knife. Place on cookie sheets about 1 1/2 inches apart.

11. Bake 10 to 12 minutes.

(If making only one cylinder of cookies, cut the following in half.)

12. Melt 1/2 cup butter or margarine and the semisweet chocolate in a double boiler or in the microwave.

13. Add 1/2 tsp mint extract to melted chocolate; mix.

14. Drizzle over warm cookies.

15. Place on wire racks, and let cool and harden completely.