Preheat your oven to 350.
In a mixer cream the butter until it is light and fluffy. Add the powdered sugar and cream some more, scraping the sides of the bowl as necessary. Stir in the vanilla extract and then the salt and cocoa powder. Mix until the cocoa powder is integrated and the batter is smooth and creamy, like a thick frosting. Add the whole wheat pastry flour and mix just until the flour is incorporated - don't overmix.
Turn the dough out onto a counter, gather it into a ball, and knead it just once or twice to bring it together nicely. Place the ball of dough into a large plastic bag and flatten it into a disk roughly 3/4-inch thick. Place the dough in the freezer for approximately 20 minutes to chill.
Remove the dough from the freezer and roll it out very thin, about 1/8-inch thick. Cut out cookies using a 1 1/2-inch cutter. Place cookies on a parchment-lined baking sheet and bake for 10 minutes. Remove the cookies from the oven and allow them to cool completely.
While the cookies are in the oven, get the coating ready. Use a double boiler to slowly melt the chocolate, stirring occasionally until it is glossy and smooth. Stir in the peppermint extract. Adjust to taste by adding a drop or two more - but don't overdo it!
Coat the cookies one at a time, dropping each cookie into the chocolate, making sure each one gets fully coated. Lift the cookie out of the chocolate with a fork allowing any excess chocolate to drip off before placing it on a parchment-lined baking sheet to dry. You want a thin, even coating of chocolate. Place the cookies in the refrigerator or freezer to set.