Cardoons are one of the oddest of the vegetable world. Not well known outside of Italy, it is grown in California and enjoys a good reputation in Italian neighborhoods. It is a relative of the Artichoke plant, a member of the thistle family. The blanched stalks are similar to celery and are eaten raw, steamed or braised with garlic, white wine and olive oil.

Here are some excellent sites for information on Cardoons and some good recipes:

http://www.hort.purdue.edu/newcrop/Crops/Cardoon.html

http://www.orst.edu/Dept/NWREC/cardoon.html

http://www.island.wsu.edu/CROPS/CARDOON.htm

http://www.sardinia.net/agritur/uk/ricette.htm
The following recipe is from this web site^
CARDOON ALLA SARDA 

INGREDIENTS 
- 1 kg. of cardoon - lemon - bread crumbs - the yolks of 4 hard-boiled eggs - parsley - oil or butter - salt - pepper 

PREPARATION 
Clean the cardoon stripping away the outer part, cut into pieces and rub with lemon or add lemon juice and then cover with cold water. In a saucepan put water and salt and bring to the boil. Add the cardoon pieces and slowly cook for 2 hours. Strain the cardoon pieces well and put them on a plate. Chop the hard-boiled eggs yolks and the parsley and cover the cardoon with them. Melt the butter and mix with the bread crumbs. Cover the cardoons with the butter and the bread crumbs and serve.