Broccoli rabe, also called rapini, is not botanically related to either broccoli or broccolini (photo courtesy Good Eggs).  Broccolini is a hybrid of broccoli and kai-lan, a Chinese chard (photo courtesy Bodecology).  Broccoli has thick stalks and large florets (photo courtesy Burpee).
1. PREHEAT the oven to 350°F.
2. WARM the olive oil and garlic in a small saucepan over low heat until the garlic is softened and aromatic, about 4 minutes.
3. BEAT the butter, broccoli rabe purée, garlic oil and salt until well blended.
4. SLICE the loaf in half lengthwise, using a bread knife. Spread the broccoli rabe butter liberally on both sides of the cut surfaces. Reassemble the loaf and wrap it in aluminum foil. Bake until hot and aromatic, 10-15 minutes.
5. CUT into 1-inch slices and serve hot or warm.
Some 15 years ago, broccoli rabe began to appear in some restaurants.
Also called broccoli rape, raab (pronounced rob), rapini, Chinese broccoli and Italian broccoli in the U.S., it then became available in produce markets. Now, it can be found at more and more quality supermarkets.
Descended from a wild herb—like many of our greens—versions of broccoli rabe originated in the Mediterranean and in China.
Broccoli rabe is not botanically related to either broccoli or broccolini.
It is sweeter than broccolini, and like broccoli, it can be eaten raw.
Although it bears the name “broccoli,” broccoli rabe tastes like a bitter and pungent form of broccoli (think broccoli crossed with mustard greens with some nuttiness).
In fact, the slender-stalk broccoli rabe is not related to broccoli, but to turnips.
That’s why the leaves look like turnip greens—broad and flat—and why the vegetable is also called Italian turnip and turnip broccoli.
Broccolini is not a young growth of broccoli, although it looks like small broccoli florets atop long, slender stems.
Rather, broccolini is a hybrid of broccoli and kai-lan, a Chinese chard (and also a cruciferous vegetable).
In Italy it is also called broccoli di cicco, an heirloom variety dating back to 1890. Cicco is a diminutive of the given name Francesco (perhaps the man who created the hybrid?).