Preheat oven to 350°F and place a rack in the center.
Fit the pie crust into a 9-inch pie plate and crimp the edges. Chill while you make the filling.
Whisk melted butter, granulated sugar, and brown sugar in a bowl until glossy and combined.
Beat in eggs one at a time, then stir in vanilla and espresso powder.
Sift cocoa, flour, and salt over the bowl. Fold just until no dry streaks remain.
Fold in chocolate chips and pecans, if using.
Spread the batter into the chilled crust and smooth the top. Shield crust edges with foil if desired.
Bake 35–40 minutes until the edges are set and the center has a slight jiggle with a shiny crust.
Cool on a rack at least 45 minutes for fudgy slices. Serve warm or at room temperature.