Sift together flour, cocoa powder and salt; stir well and set aside.

In large mixer bowl, cream butter until light and fluffy.

Gradually add icing sugar, beating until smooth. Add vanilla. Gradually add flour mixture, stirring well to combine.

Chill for at least 1 hour.
 
Divide dough into three portions and roll out on a lightly floured surface to a little less than 1/4 inch (5 mm) thickness. Cut out shapes with a floured cookie cutter. Place on ungreased foil-lined baking sheets. Bake at 350ºF (180ºC) for 10 to 12 minutes. Makes about 3 dozen cookies. 

Tips: 
I tested this recipe on a very hot day, when the butter turned almost to oil. Chilling didn't do the trick, so I simply shaped the dough into 1-inch (2.5 cm) balls and pressed them down with a fork. They were just as tasty and saved the rolling procedure.

Dough can also be shaped into two 1 1/2-inch (4 cm) rolls and chilled, then sliced to the same thickness and baked