Sift together powdered sugar and 2 tablespoons cocoa. Set aside.
Beat butter at medium speed with an electric mixer until creamy. Add flour and next 3 ingredients, beating until blended. Stir in pecans. (Dough will be stiff.) Shape into 1-inch balls, and place on ungreased baking sheets.
Bake at 400° for 10 minutes. Remove cookies to wire racks, and cool slightly. Roll warm cookies in powdered sugar mixture, and cool completely on wire racks.