Cream butter, shortening and brown sugar, using an electric mixer. Add egg and molasses; mix well. Gradually add in flour, baking soda, salt and cinnamon.
Roll dough into 1-inch balls, then roll the balls in 1/2 cup white sugar. Place balls 2 inches apart on an ungreased baking sheet. Flatten with a flat-bottomed drinking glass.
Bake at 350ºF for 10 to 12 minutes, or until cookies are set and tops are cracked. Cool on wire rack.
