Cream together the butter, shortening, sugars, egg and vanilla by hand (no mixer!)
In a separate bowl mix together the flour, baking soda, cream of tartar and salt.
Add the dry mixture to the butter and sugar mixture and combine.
Cover bowl and refrigerate for 1-2 hours.
Preheat oven to 350 degrees Fahrenheit.
Roll dough into walnut-sized balls.
Dip half of ball in cold water and then in white sugar to form a glaze on top of the cookie. Place onto greased cookie sheet.
Bake 9 to 11 minutes or until cookies are just barely turning brown around the edges. Do not over bake.