1. Melt chocolate and set aside to cool. Mix together flour, cocoa powder, cinnamon, ginger, cayenne, nutmeg, baking powder, and salt into a bowl.
2. With an electric mixer with the paddle attachment, beat butter and brown sugar on medium speed until pale and fluffy. Mix in eggs and vanilla and then the melted chocolate. Reduce the speed to low and mix in the flour mixture in two batches alternating with the milk. Then add the beer. Divide dough into three or four equal pieces and wrap them in plastic wrap and refrigerate until firm (2 hours to overnight).
3. Preheat oven to 350F and divide each piece into sixteen 1 inch balls. Roll in the granulated sugar and then the powdered sugar and place on a baking sheet with parchment paper. About 2 inches apart because they will spread.
4. Bake until the surfaces crack, about 14 minutes. Rotate the sheets halfway through. Let cool on wire racks. Cookies can be stored for up to 3 days.
These are quite possibly my favorite cookies. I get tons of requests to make these because they are rich, warming, and crunchy on the outside with a soft middle. They might be the most perfect cookie, ever.