Beat butter in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. add brown sugar, cocoa, instant coffee, baking soda and cinnamon; beat till combined, scraping sides of bowl occasionally. Beat in egg whites and yogurt till combined. Beat in a 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. Bake in a 350* F. oven for 8 to 10 minutes till edges are firm. Transfer to wire racks; cool. Makes about 40.