Yes indeed,, many years ago when I still lived in UK, my Mum would buy a Paris Brest as a special treat for me from Maison Lyons, Marble Arc, London.
It was delicious but strangely enough I have never thought to make one, the one from Maison Lyons was the choux pastry, filled with whipped cream with a light dusting of confectioner sugar and toasted slivered almonds on the top, Mmmmm, I can taste it now. :-))) qahtan

oh YUM! Is it hard to make such pastry?

If you go to the site below it will give you detailed instructions on how to make the paste, from there it's your choice what you fill with... qahtan

http://www.theworldwidegourmet.com/relais/techniques/pates/pate-choux.htm

to make a good paste: but I don't like the formula that you have linked. The professional forumal, infact, prescribe weight off eggs and not thei number. If you like my cake, I can write the recipe: in english, if you help me to translate it. So, I cant write the english version too on my website...
I have just written this page: http://www.scuoladipasticceria.it/index.php?T=basta_bigneen
Can you see if is ok? Thank's.
:D

however, my formula is:
500 gr of water,
175 gr of butter
250 gr of flour ( low gluten content),
600 gr of entire eggs
13 gr salt

Place water, butter and salt in a medium saucepan and bring slowly to a simmer. Turn off heat and add the flour all at once. Stir vigorously with a wooden spoon until that the paste is detached from the wall. Return to medium heat to dry the paste.
Remove from heat,let cool a bit and incorporate eggs one to the time with a wooden spoon or the paddle. Load mixture into pastry bag with a round tip and pipe out as required on a parchment paper . Bake choux pastry at 220° C (425°F) until fully puffed and start to show some color. Then, reduce the 190° (375°F) and bake about 10 or 12 munutes longer. A wooden skewer inserted into the center should come out almost dry.

And these are the photos: