Blend butter, vanilla and salt. Beat in sugar until smooth & fluffy. Stir in flour. Turn down mixer and add chocolate chips until just mixed in. Press dough into cookie sheet with sides, cover bottom of cookie sheet. Press chopped pecans into dough, if desired. Bake at 350° for 25 min - watch that edges don't get too brown. Let cool and break into cookie-sized pieces (like brittle). This can also be kept whole and frosting used to write a message on the top. I grew up on this stuff, it's the best and easiest!