In a small mixing bowl, cream the butter, shortening and sugars. Beat in egg yolk and vanilla; mix well. Combine the flour, baking soda and salt; gradually add to creamed mixture and mix well. Stir in chips and pecans. Shape into a 9-in. roll; wrap in plastic wrap. Refrigerate overnight.
Unwrap and cut into 1/4-in. slices. Place 2 inches apart on ungreased baking sheets. Bake at 375° for 8-10 minutes or until edges are golden brown. Cool for 2 minutes before removing to wire racks to cool completely.