Shell the fava beans and blanch in boiling salted water for 2 minutes*. Drain and, when cool enough to handle, slip off the tough outer skin of the beans. Discard skins and reserve beans on the side.

*(If using frozen blanched favas, you can skip this step and go straight to slipping off the outer skin.)

Heat a large pot of salted water to a boil and cook the fettuccine, stirring often, until al dente. Drain and reserve 3/4 to 1 cup of the cooking liquid separately.

While the pasta is cooking, heat the olive oil in a large skillet over medium-high heat. Add the onion and pancetta and cook until the onion is soft and the pancetta begins to crisp, about 7 minutes. Add the garlic and cook for 1 minute. Add the favas and escarole to the pancetta and cook until the beans are tender, about 5 minutes.

Add the drained pasta, 3/4 cup of the reserved cooking liquid, and heavy cream to the fava mixture and cook, tossing to mix thoroughly, until everything is heated through. Add the remaining cooking liquid if necessary. Season to taste with salt and freshly ground black pepper. Garnish with 2 tablespoons grated Pecorino Romano and serve immediately. Pass the extra grated cheese at the table.