Preheat oven to 400 °F (205 °C).
Roll out flaky pastry to a circle, 9 inch (23 cm) wide by 1/4 inch (0.5 cm) thick.
Butter, then moisten a cookie sheet.
Transfer pastry to cookie sheet.
Prick with a fork.
Brush with beaten egg.
Using a pastry bag with a plain nozzle, pipe a crown of puff paste along edge of pastry crust.
Starting from the center, spiral puff paste onto pastry.
Brush with beaten egg.
Bake in oven 20 minutes.
Let cool.
In a bowl, mix Grand Marnier, half the Chantilly cream and all of the custard.
Set aside.
With a pencil, punch a hole under each puff.
Using a pastry bag with a plain nozzle, stuff with Grand Marnier cream.
Spread a layer of Grand Marnier cream into the center of cold cake.
Dip puff bottoms in chocolate.
Set around crown, reserving 1 puff for center decoration.
Arrange peaches over cream layer.
Cover with remaining Grand Marnier cream, then Chantilly cream.
Sprinkle with orange peel.
Place last puff in the center of Saint honore.
Dust with icing sugar, if desired.