In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add brown sugar, cocoa powder, milk, vanilla, and baking soda. Beat until combined, scraping sides of bowl occasionally. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour. Shape dough into a smooth ball. If necessary, cover and chill dough about 30 minutes or until dough is easy to handle.

Preheat oven to 375 degrees F. Divide dough in half. On a lightly floured surface, roll a portion of the dough 1/4 inch thick. Using a 2-1/2x1-3/4-inch diamond-shape cutter, cut out dough. Place cutouts 2 inches apart on ungreased cookie sheet. Bake in preheated oven for 6 to 8 minutes or until edges are firm. Cool for 1 minute on cookie sheet. Transfer to a wire rack and let cool completely.

In a small saucepan, combine chocolate pieces and shortening. Cook and stir mixture over low heat until melted. Dip half of each cookie into chocolate, allowing excess to drip off. Place on waxed paper. Sprinkle each cookie with crushed candy canes. Let stand about 30 minutes or until chocolate is set. Makes about 50 cookies.

Layer undipped cookies between waxed paper in an airtight container; cover. Store at room temperature for up to 3 days. Or freeze undipped cookies for up to 3 months; thaw, dip, and sprinkle as directed above.