4 tablespoons extra-virgin olive oil, divided
3 garlic cloves, peeled, flattened
1 medium onion, chopped
3 ounces thinly sliced pancetta, chopped
1 teaspoon fennel seeds, crushed
1/4 teaspoon dried crushed red pepper
1 large bunch broccoli rabe (also called rapini; generous 1 pound), stems sliced
1/2 inch thick, tops cut into 2-inch pieces
1 cup water
1 8.8-ounce package dried pappardelle pasta
1 cup freshly grated Pecorino Romano cheese, plus additional for serving
1/2 cup pine nuts, toasted
Heat 2 tablespoons oil in heavy large skillet over medium-high heat. Add garlic and cook until golden brown, stirring frequently, about 3 minutes. Discard garlic. Add onion, pancetta, and fennel seeds to skillet; sauté until onion is tender and pancetta begins to brown, about 8 minutes.
Add dried crushed red pepper, then broccoli rabe stems and cook 4 minutes to soften slightly, stirring occasionally. Stir in broccoli rabe tops, sprinkle with salt, and add 1 cup water.
Cover and cook until stems and tops are tender, about 5 minutes. Season to taste with salt and pepper. Meanwhile, cook pasta in large pot of boiling salted water until just tender but still firm to bite. Drain pasta, reserving 1 cup cooking liquid. Add pasta to skillet with broccoli rabe and stir over low heat to combine, adding reserved cooking liquid by tablespoonfuls to moisten if necessary.
Stir in remaining 2 tablespoons oil and 1 cup cheese. Season to taste with salt and generous amount of pepper. Transfer to shallow bowl. Sprinkle with pine nuts and serve, passing additional cheese separately.