In the kitchen, you can prepare Puntarelle raw seasoned with salt, oil and vinegar, or prepared Roman style... by cutting the bottom root off the head, then peeling away the dirty outer leaves as you would a head of lettuce. It's best to taste one of the inner leaves to see if they are too bitter or not. If you want less bitter taste, peel off a bit more. The best parts are toward the center--with feathery tops. You cut them from the base and then slice them lengthwise like a julienne cut. Soak them in a bowl of cold water until they curl up. You can then dress your insalata with olive oil, vinegar, salt, pepper and some garlic. Some anchovies with a squeeze of lemon works well, too. You can also use them in cooked recipes, as in a frittata. The leaves can be sautéed with sausage and orecchiette as is done in Puglia, or winter soups with beans and garlic.
They can be difficult to find in the States, but not impossible. Being grown in California, they are appearing more and more in gourmet green grocers in the larger cities.
Yes, essentially they are all the same... aside from the fact that there are many varieties grown and whether or not the plants were overwintered (sweet) or not (bitter). The plant has more in common with mustard greens than broccoli (perhaps a distant relation), yet in Italy, Cime di Rape translates as Turnip Greens, even though they have little to do with turnips, either. Basically, Rapini looks like a bunch of turnip or mustard greens with bunches of small, broccoli looking florets. In the U.S. you can find several varieties sold under the name Broccoli Rabe ("raab").
Rapini is commonly used in mostly southern Italian cuisine and has a bitter taste (unless picked during the winter or early spring). The leaves, buds, and stems are all edible. The trick to calming its bitterness is boiling as you do pasta--in salted water. After draining or squeezing out excess water, you can add olive oil, garlic, and some dried pepperoncini. Use Rapini for in pasta sauces, omelettes, frittatas, soups and polenta.
Cardoon leaf stalks can be served steamed or braised, and taste very much like artichokes with some bitterness. Especially during the Christmas holiday, people from the Abruzzi region serve a traditional cardoon soup with meatballs in chicken broth. Often an egg is mixed into the soup (called stracciatella, my Dad used to love this). There are even casserole dishes which feature baked cardoon with onions, cheese or a bechamel sauce.
The most common way to prepare after boiling is to dress with olive oil, salt and lemon for a refreshing side dish with fish or chicken.
Romanesco is in season during from late summer to early fall, and it can often be found at local farmers’ markets in the eastern coast of the United States. Although it looks like cauliflower with a similar texture, in fact, it tastes like broccoli. And as with most Italian recipes, simple is best. Boiled or steamed, florets tossed with pasta, lemon, olive oil and pepper and you have a great meal.