In a medium bowl, cream together butter and sugar until smooth. Stir in egg yolk and vanilla. Gradually stir in the flour until just blended, then mix in crushed potato chips and pecans. Drop by rounded spoonfuls onto ungreased cookie sheets. Criss-cross the top using a fork dipped in water.
Bake 12 to 14 minutes in preheated oven, or until edges are lightly browned. Cool on baking sheets.
