Preheat oven to 350 degrees. Line a cookie sheet with wax paper. Mix flour, soda, and salt together in medium bowl. Cream together butter and sugars, shortening, eggs, and vanilla in large mixing bowl. Stir in peanut butter. Ad flour mixture and stir until blended. Drop dough by teaspoonfuls onto cookie sheet. Using a fork dipped in flour, flatten each cookie slightly with a crisscross pattern. Bake for 8-10 minutes or until slightly golden around edges. Do not overbake.