Whisk together egg yolks and flour; add the milk, sugar, and vanilla. In a heavy bottomed saucepan, stir over medium heat until mixture thickens, and coats the back of a spoon. Be careful not to allow the mixture to scorch the bottom of the pan. Reduce heat if necessary.
Finely crush the Nilla Wafers in a plastic bag using the back of a spoon or rolling pin (or use a blender). Line the bottom of a pie pan evenly with crushed crackers, reserving a few spoonfuls to sprinkle on top.
Refrigerate several hours before serving. Submitted by: Ken Bryant
