In a large bowl, using a wire whisk, mix together the flour, cornmeal, sugar, cocoa powder, and salt. With your fingers, rub in butter until mixture comes together when squeezed with your hand. If baking with ring molds, form the dough into a cylinder of the desired length and wrap tightly in parchment paper. I formed mine into a cylinder that was 1 3/4-inches in diameter. Refrigerate overnight. When ready to bake, set a rack on the bottom third of the oven and preheat to 325°F. Line a sheet pan or two with parchment paper. Cut the log into ⅛- ¼ inch disks (the thickness is your option) and place on the parchment paper spacing about 2-inches apart.  Check the cookies about 15 minutes after they go in the oven.  Total baking time should be about 20-25 minutes depending on thickness.  Once the cookie is set, remove to a cooling rack and let them cool completely.

The dough can be frozen, but first, wrap tightly in parchment paper and then in plastic wrap.