Preheat oven to 400 °F
In a large bowl, cream together ½ c solid shortening, ½ c margarine, ½ c brown sugar, ¾ c white sugar, 1 egg, and ½ tsp vanilla until smooth.
Beat 6-8 minutes with an electric mixer until light and fluffy.
Sift together 2 c flour, 1 tsp baking soda, ½ tsp salt, and 1 tsp cream of tartar.
Add to creamed mixture gradually, stirring until well blended.
Fold in 6 oz semi-sweet chocolate chips.
Drop by the teaspoonful onto a lightly greased cookie sheet.
Bake for 10-12 minutes.