In a medium saucepan, combine condensed milk, pecans and vanilla. Cook over medium heat, stirring constantly, until mixture thickens and begins to pull away from the sides of the pan, about 10-12 minutes.Spread nut mixture in bottom of baked pie shell. In a small saucepan, combine chocolate chips and cream.Cook over medium heat, stirring constantly until chocolate melts and combines with cream. Pour over pie filling: chill. Remove from refrigerate one hour before serving. Ultra rich!!!!