Combine first 5 ingredients in a large mixing bowl; mix at medium speed with an electric mixer for 2 minutes. Add egg; mix well and set aside.
Stir together flour, soda and salt; add shortening mixture, mixing well. Fold in chocolate. Shape dough into 1/2-cup balls; press down to form 3 1/2-inch round discs. Arrange 3 inches apart on ungreased baking sheets.
Bake at 375° for 15 minutes. Cool for 5 minutes; remove to a wire rack to cool completely.