Preheat the oven to 375 degrees F (190 degrees C). Grease cookie sheets.
In a medium bowl, cream together the brown sugar, white sugar, margarine and shortening until light and fluffy. Stir in yogurt and vanilla. Combine the flour, baking soda, and salt; stir into the creamed mixture until incorporated, then mix in chocolate chips. Drop by rounded teaspoonfuls 2 inches apart onto the prepared cookie sheets.
Bake for 8 to 10 minutes in the preheated oven, until the edges begin to brown. Cool for a minute on the cookie sheets before removing to wire racks to cool completely.