In a large saucepan heat the 1/4 cup olive oil over medium-high heat. Add the onion and cook until just beginning to caramelize around the edges, 5 to 7 minutes. Add the garlic and cook for 1 minute, stirring constantly. Add the broccoli rabe and cook, stirring, until just wilted, about 3 minutes. Add the cannellini beans, chicken broth, crushed red pepper and basil and cook at a simmer, uncovered, until the liquid has reduced slightly and the beans are just beginning to break apart, about 15 minutes. The sauce should be brothy. Remove from the heat and season with salt and freshly ground black pepper.
When ready to serve, transfer the warm pasta to a large bowl. Add half of the sauce and toss to combine. Serve the pasta in shallow bowls, with more sauce ladled over the top. Sprinkle each serving with some of the crispy pancetta and drizzle with extra-virgin olive oil, to taste. Pass the cheese at the table for guests to add at their own discretion.