Preheat oven to 375 degrees. Mix sugars, margarine, vanilla, and egg in large bowl. Stir in flour, baking soda and salt (dough will be stiff). Stir in chocolate chips. Drop dough by rounded teaspoonfuls about 5 cm apart onto ungreased cookie sheet. Bake 8 to 10 minutes, or until light brown (centers will be soft). Cool slightly; remove from cookie sheet. Cool on wire rack.