1. Whisk flour, cocoa powder, and salt in medium bowl to blend.
2. Using electric mixer, beat butter or margarine in large bowl until smooth.
3. Beat in peppermint extract and vanilla extract.
4. Beat in sugar in 3 additions.
5. Add egg and beat until blended.
6. Add dry ingredients and beat just until blended (dough will be sticky).
7. Divide dough between 2 sheets of plastic wrap.
8. Using plastic wrap as aid, form dough on each into 2-inch-diameter log.
9. Wrap with plastic and refrigerate dough until well chilled, at least 2 hours.
10. (Dough can be prepared 1 day ahead. Keep refrigerated.)
11. Preheat to 350. Line 2 baking sheets with parchment paper.
12. Unwrap cookie dough logs; roll briefly on work surface to form smooth round logs.
13. Cut logs crosswise into 1/4-inch-thick rounds. Place rounds on prepared baking sheets, spacing 1 inch apart.Cut logs crosswise into 1/4-inch-thick rounds. Place rounds on prepared baking sheets, spacing 1 inch apart.
14. Bake cookies until tops and edges are dry to touch, about 15 minutes. Transfer baking sheets with cookies to racks; cool completely.
15. Stir chocolate in top of double boiler set over simmering water until melted and smooth.
16. Remove from over water. Cool melted chocolate until slightly thickened but still pourable, about 10 minutes.
17. Dip fork into melted chocolate, then wave fork back and forth over cookies, drizzling melted chocolate thickly over cookies in zigzag pattern.
18. Refrigerate cookies on baking sheets until chocolate is set, about 10 minutes. (Cookies can be made 1 week ahead.
19. Refrigerate in airtight container between sheets of parchment paper or waxed paper.)
20. Makes about 3-1/2 dozen.

Just like thin mints!!