Step 1

Cream together the butter, sugar, brown sugar and vanilla until light, about 2 minutes.

Step 2

In a medium bowl, whisk together the flour, cocoa powder, soda and salt. If there are any lumps of cocoa powder, sift the dry ingredients before adding to the butter.

Step 3

Add the dry ingredients to the butter mixture and mix just to combine. Add the milk and mix just to combine.

Step 4

Form the dough into two 1 1/2-inch-thick logs. Wrap well in plastic wrap and refrigerate for at least an hour.

Step 5

To bake: Preheat the oven to 350 degrees F and line 2 baking sheets with parchment.

Step 6

Slice the log of cookie dough into 1/8-inch-thick coins.

Step 7

Arrange on the baking sheets with about 1 1/2 inches between the cookies. Bake for 8 minutes and then rotate the trays back to front and switch from top and bottom racks. Bake for another 2 minutes or until they are dry looking and firm. Because the cookies are so dark, you can't go by color on these.