How to Make It
Make crust: In a food processor, pulse dry ingredients. Pulse in butter until crumbly. Add 5 Tbsp. ice water; pulse until dough comes together, adding more water if needed. Knead, shape into a disk and wrap in plastic; chill 15 minutes.
Make filling: Whisk cream, espresso powder, cinnamon, salt and cornstarch. Bring to a boil, whisking, 3 minutes. Lower heat; cook 2 minutes.
Beat yolks lightly. Whisk as you pour in 1/2 cup of cream mixture. Pour back into pan and cook, whisking, 2 minutes; mixture will be thick. Pour into a clean bowl. Add chocolate chips and butter; let stand 2 minutes. Stir until chocolate has melted. Place plastic wrap directly on surface and chill 35 minutes.
Preheat oven to 400ºF. Roll out dough into a 12-inch circle; fit into a 9-inch pie plate. Trim edges of crust, leaving a 1-inch overhang. Turn overhang under; crimp edges. Prick bottom of crust all over with a fork. Place foil on crust and fill shell with pie weights. Bake 15 minutes. Remove foil; bake 15 to 20 minutes longer, until crust is brown. Cool on a wire rack.
Beat filling with an electric mixer until smooth. In a separate bowl, beat 1/2 cup heavy cream until stiff peaks form; fold cream into filling. Spoon into cooled pie shell and chill 2 hours.
Make topping: Whip cream with confectioners' sugar and mound on top of pie. Grate chocolate on top.