Cardoon and artichoke are members of the thistle family and they are edible.
They look so alike, but with cardoons you eat the stalks and as you probably know it is the artichoke flower that is eaten.
Well actually, when you eat an artichoke you eat the flower before it has fully formed. If you wait till it is in full bloom I do not think it will have much flavour, as the seeds are set in the artichoke bottom which is the best bit. Presumably the seeds will take all it goodness out of it.
The cardoon sets the same type of flowers, but it does not develop a thick bottom like its cousin. In this plant the stalks are the show stopping ingredient. The plant should be blanched – grown in the dark like rhubarb – which makes the stalks very tender. You prepare the stalks like celery, taking the stringy bits out.
I use an 18th century recipe from Hannah Glass. She suggests you simmer them till tender in chicken broth, then put them in a dish and grate parmesan over. With a red hot salamander you make the cheese melt. . . . . you may use a grill!