Preheat the oven to 325 F. Melt butter and dark chocolate together in the microwave and whisk until smooth. Cool the mixture to room temperature. Beat brown sugar, granulated sugar, vanilla and eggs until well combined. Pour in cooled chocolate and mix evenly. Sift together flour, baking cocoa, cinnamon, chili powder, cayenne pepper and salt.
Add dry ingredients to chocolate batter and mix until well combined. Fold in chocolate chips. Make balls out of the dough and place on a baking sheet.
Bake for 14 minutes. Remove cookies from baking sheet and let cool.
Yields 8-10 servings