In a small bowl, combine the flour, cocoa, baking powder and salt. Set aside.
Then, in a mixing bowl, beat together the butter, margarine and brown sugar until creamy and smooth. Beat in the egg and vanilla until well combined.
Add the flour mixture and mix well.
On a piece of plastic wrap, place the cookie dough in the middle and wrap up into a log.
Refrigerate for at least one hour, preferably overnight but not longer than 12 hours.
When cooled, unwrap the cookie dough and slice into 1/4-1/2 inch slices. Soften the cookie dough by lightly rolling it in your hands. Flatten it and place an unwrapped Hershey Kiss in the middle. Wrap the cookie dough around the Hershey Kiss and roll into a ball. Place on a lightly greased cookie sheet. Repeat with the remaining cookie dough.
Bake in a 350F degree oven for 10-12 minutes.
Remove the cookie drops from the oven and immediately place in a shallow dish with granulated sugar. Caution: Cookie will be hot!! Roll the cookie around until it is covered with sugar. Place on a cooling rack to cool.
Best enjoyed when slightly warm!!