Arrange an oven rack in the center of the oven. Preheat oven to 425°F (218ºC).
Roll pie crust out, on a very lightly floured surface, into a 12-inch circle. Fit pie crust in a 9-inch standard pie plate. Fold edges under, and decoratively crimp or pinch the edges. Chill until crust is firm, at least 1 hour.
Line the pastry with aluminum foil or parchment paper. Fill with dried beans or pie weights. Bake at 425°F (218ºC), on the arranged oven shelf for 5 to 7 minutes. Remove weights and foil; bake for 2 more minutes or until golden. Cool on a wire baking rack.
In a microwave-safe mixing bowl, add evaporated milk (2/3 cup), chocolate morsels (6 ounces), espresso powder (1/2 teaspoon), and butter (2 tablespoons). Microwave on high for 1 to 1 1/2 minutes, whisking at 30-second intervals, until the mixture is smooth and melted.
Add sugar (1 cup) and flour (2 tablespoons) to the chocolate mixture and whisk to combine.
Add eggs (2) to the mixture, 1 at a time, whisking just until blended after each addition.
Add vanilla (2 teaspoons) and salt (3/4 teaspoon) and whisk to combine.
Add pecans (1 cup), if using, and stir until evenly combined.
Add mixture to pie shell. Bake in preheated oven (Still at 425ºF (218ºC)) until the pie is set in the center, about 35 to 40 minutes. If the edges of the crust are browning too quickly, apply a pie shield. Cool for 10 minutes before serving.