It's usually dusted with black pepper and herbs, then rolled up like a jelly roll and sliced into pinwheels.
Savoy cabbage looks like regular cabbage that sat in the bath too long.
The large, deeply wrinkled leaves have a milder flavor, one that's improved by frost, so it tastes better in the winter. You could substitute plain cabbage or kale. Add the diced pancetta and cook for about 5 minutes, then add the chopped onion. Cover, reduce the heat, and cook for another 10 minutes or so. When it still has a nice bite, and may in fact seem a little undercooked, turn off the heat and drain, reserving a cup or two of the pasta cooking water.