In a large bowl, cream together the sugars and butter until light and fluffy.
Add eggs, one at a time, beating well after each one. Stir in vanilla.
In a separate bowl, sift together the flour, cocoa, baking soda, salt, and chili powder.
Gradually stir the dry ingredients into the creamed mixture.
Mix in the chocolate chips and nuts, if desired.
Drop by teaspoonfuls onto ungreased baking sheets.
Bake for 10 to 12 minutes, or until cookies are set. Allow to cool on baking sheets for a few minutes before transferring to a wire rack to cool completely.
Interesting Facts
Chili powder is a blend of spices, usually including cumin, oregano, garlic, and chili peppers.
Dark brown sugar has a richer flavor than light brown sugar because of the molasses content.
Semi-sweet chocolate chips are made with a combination of sugar, cocoa butter, and chocolate liquor.