Bring 1 cup water, grits, and ⅛ teaspoon salt to a boil over medium heat. Cook, stirring often, until thickened. Remove from heat, and let cool for 10 minutes.
Preheat oven to 375°. Place piecrust in a 9-inch pie pan, and crimp edges as desired.
In a medium microwave-safe bowl, add evaporated milk, butter, chocolate, sugar, and flour; heat on high for 1 minute. Remove from microwave, and whisk until smooth. Whisk in grits, eggs, vanilla, and remaining ½ teaspoon salt. Pour into prepared pie crust.
Bake until puffed and set in center, 25 to 30 minutes. Serve warm or cold with whipped cream.