Step 1

In a small bowl, sift together the flour, black cocoa powder and salt. Set aside.

Step 2

In mixing bowl, cream together the butter and the sugar. (Electric or hand mixer is great here.)

Step 3

Mix in the vanilla and milk until fully combined.

Step 4

Mix in the dry ingredients, just until fully absorbed.

Step 5

Press the dough into itself and shape into a log, approximately 1½ inches in diameter. Best to roll the log in parchment paper. Refrigerate 30-60 minutes, then move the log into plastic wrap and roll the log to get it as round as possible. Refrigerate at least another hour.

Step 6

Preheat oven to 350° F.

Step 7

Beat the egg. Egg wash the log of cookie dough. Roll in sugar to coat well. Cut slices at least ¼ inch thick and no thicker than ½ inch. Place on a parchment lined baking sheet 2 inches apart. Bake 17-20 minutes. Cool completely.