01 -
Place a rack in the lower third of the oven and heat to 375°F. Set a deep 9-inch pie plate on the counter.
02 -
Fit the crust into the pie plate. Brush the edge with beaten egg, sprinkle with coarse sugar, prick the bottom with a fork, then line with parchment and fill with pie weights. Chill for 10-15 minutes.
03 -
Bake the weighted crust for 20 minutes. Remove the parchment and weights, then bake 5 minutes more until lightly golden. Reduce the oven to 350°F.
04 -
Whisk the eggs and sugar in a large bowl until smooth and glossy. Whisk in cocoa powder, espresso powder, salt, melted butter, vanilla, and hazelnut liqueur if using.
05 -
Fold in the chopped chocolate. Pour the filling into the warm crust and smooth the surface with a spatula.
06 -
Bake at 350°F for 45-55 minutes, until the top is puffed and crackled and the center still has a gentle wobble. Shield the crust edge with foil if it browns too fast.
07 -
Cool the pie for 20-30 minutes. Beat the heavy cream, maple syrup, vanilla, and hazelnut liqueur if using until soft peaks form.
08 -
Slice the pie while warm and top each piece with hazelnut whipped cream. Refrigerate leftovers after cooling fully.