Instructions

for the dough

Grate 2 tablespoons chilled unsalted butter on large holes of box grater and place in freezer. Cut remaining 8 tablespoons chilled unsalted butter into ½-inch cubes.
Pulse 3¾ ounces all-purpose flour, 1 tablespoon sugar, and ½ teaspoon table salt in food processor until combined, 2 pulses. Add cubed butter and process until homogeneous paste forms, about 30 seconds.
Using your hands, carefully break paste into 2-inch chunks and redistribute evenly around processor blade. Add remaining 2½ ounces all-purpose flour and pulse until mixture is broken into pieces no larger than 1 inch (most pieces will be much smaller), 4 to 5 pulses.
Transfer mixture to medium bowl. Add grated butter and toss until butter pieces are separated and coated with flour.
Sprinkle 2 tablespoons ice water over mixture. Toss with rubber spatula until mixture is evenly moistened. Sprinkle remaining 2 tablespoons ice water over mixture and toss to combine. Press dough with spatula until dough sticks together.
Transfer dough to sheet of plastic wrap. Draw edges of plastic over dough and press firmly on sides and top to form compact, fissure-free mass. Wrap in plastic and flatten to form 5-inch disk. Refrigerate dough for at least 2 hours or up to 2 days.
Let chilled dough sit on counter to soften slightly, about 10 minutes, before rolling. (Wrapped dough can be frozen for up to 1 month. If frozen, let dough thaw completely on counter before rolling.)
Roll dough into 12-inch circle on well-floured counter.
Roll dough loosely around rolling pin and unroll it onto 9-inch pie plate, leaving at least 1-inch overhang around edge. Ease dough into plate by gently lifting edge of dough with your hand while pressing into plate bottom with your other hand.
Trim overhang to ½ inch beyond lip of plate. Tuck overhang under itself; folded edge should be flush with edge of plate. Crimp dough evenly around edge of plate using your fingers.
Refrigerate dough‑lined plate until firm, about 30 minutes. Adjust oven rack to middle position and heat oven to 350 degrees.
Line chilled pie shell with aluminum foil, covering edges to prevent burning, and fill with pie weights. Bake until edges are set and just beginning to turn golden, 25 to 30 minutes.
Remove foil and weights, rotate plate, and continue to bake until golden brown and crisp, 10 to 15 minutes longer. If crust begins to puff, pierce gently with tip of paring knife.
Let crust cool completely in plate on wire rack, about 30 minutes.

for the filling

Using either stand or hand mixer, whisk 1 cup chilled heavy cream on medium-high speed, until stiff peaks form, 1 to 3 minutes. Transfer whipped cream to bowl and refrigerate.
Microwave 8 ounces bittersweet chocolate in medium bowl at 50 percent power, stirring often, until melted, 1½ to 2 minutes.
Bring 1 inch water to simmer in medium saucepan over medium heat. In heatproof bowl, combine 3 large eggs, ¾ cup sugar, and 2 tablespoons water. Place bowl over barely simmering water, and using hand mixer, beat until mixture is thickened and registers 160 degrees, 7 to 10 minutes.
Remove bowl from heat and continue to beat egg mixture until fluffy and cooled to room temperature, about 8 minutes.
Add melted chocolate and 1 tablespoon vanilla extract to egg mixture and beat until incorporated. Add 8 tablespoons softened unsalted butter, cut into ½-inch pieces, a few pieces at a time, and beat until well combined. Using spatula, fold in whipped cream until no streaks of white remain.
Transfer filling to pie shell and refrigerate until set, at least 3 hours and up to 24 hours. Cut into wedges and serve with lightly sweetened whipped cream.