Whisk sugar, cocoa, flour, and espresso powder (if using) and salt together. Pour butter and evaporated milk into sugar and cocoa mixture and beat on high speed. Add vanilla and eggs. With mixer speed on high speed, mix for approximately 2-3 minutes to lighten.
Pour mixture into 9 inch unbaked pie shell and bake for about 55 minutes. The center of the pie will be a bit soft. Allow to cool on a wire rack for at least an hour before slicing. The pie will continue to set as it cools.
Chocolate Chess Pie Recipe https://addapinch.com/chocolate-chess-pie-recipe/