Beat butter in a large mixing bowl with an electric mixer on medium to high speed
for 30 seconds. Add brown sugar, cocoa powder, coffee granules, baking soda and
cinnamon; beat until combined, scraping sides of bowl occasionally. Beat in egg
whites and yogurt until combined. Beat in as much of the flour as you can with the
mixer. Stir in remaining flour with a wooden spoon.
Place granulated sugar in a small bowl. Drop dough by teaspoons into sugar and
roll into balls. Place balls 2 inches apart on an ungreased cookie sheet.
350 degrees F for 8 to 10 minutes until edges are firm.