01 -
Set oven temperature to 350°F and position a rack in the lower third.
02 -
In a large bowl, mix the warm melted butter with granulated sugar briefly, then let rest for 5 minutes to begin dissolving the sugar.
03 -
Whisk the butter and sugar vigorously for 30 seconds, then add the egg, egg yolk, water, and vanilla extract. Whisk again for 30 seconds until combined.
04 -
Sift cocoa powder, powdered sugar, flour, and kosher salt over the wet mixture. Gently fold using a spatula or wooden spoon until glossy and homogeneous.
05 -
Stir in chocolate chips and walnuts evenly throughout the batter.
06 -
Pour the batter into the frozen pie crust and spread evenly. Lightly spray a sheet of foil with nonstick spray and cover the pie without touching the batter.
07 -
Bake on the lower rack for 25 minutes with foil cover in place.
08 -
Remove foil carefully and continue baking uncovered for 20 to 30 minutes until the pie reaches desired firmness—less time for a fudgier texture.
09 -
Transfer to a wire rack to cool. Serve slightly warm or at room temperature; chill for a firmer texture. Accompany with optional toppings if desired.