To Make Crust: In a medium bowl, combine graham cracker crumbs, brown sugar, and cinnamon. Mix well, then stir in softened butter or margarine. Mix until all ingredients are thoroughly combined.
Generously grease an 8 inch pie pan. Press graham cracker mixture evenly into pan. Chill until ready to use.
To Make Filling: In a heavy saucepan, mix together sugar, flour, and salt. Gradually add milk, stirring well. Add egg yolks and whisk until mixture is smooth. Cook over medium heat, stirring constantly, until mixture thickens. Stir in vanilla extract and allow mixture to cool.
Pour cooled filling into crust and chill before serving.
