1 pound penne pasta
1 teaspoon olive oil
2 medium onions, cut into small dice (about 2 cups)
1 red bell pepper, stemmed, seeded and cut into medium dice (about 1 cup)
1⁄2 teaspoon salt, plus more for the pasta water
1⁄2 teaspoon freshly ground black pepper
1 1⁄2 pounds sweet Italian sausage, casings removed (or bulk sausage)
2 teaspoons minced garlic
1 bunch escarole or mustard greens, rinsed, stemmed and torn into bite-size pieces (about 8 cups)
1⁄2 cup grated Parmigiano-Reggiano cheese
1⁄4 teaspoon crushed red pepper
2 tablespoons extra-virgin olive oil
Bring a large pot of salted water to a boil. Add the penne and cook until just tender, about 11 minutes. Drain the pasta in a colander, reserving 1 cup of the cooking water, and set aside.
While the water is heating and the pasta is cooking, heat the olive oil in a 14-inch saute pan over medium heat. Add the onions, bell pepper, 1/2 teaspoon salt, and black pepper, and cook until the vegetables are soft, about four minutes.
Add the sausage and cook, breaking the pieces up with the back of a wooden spoon, until browned, six to eight minutes. Add the garlic and escarole, and cook for 5 minutes longer.
Add the cooked pasta and the reserved cooking water, and stir gently to combine. Simmer just until everything is heated through, about 2 minutes.
Transfer the mixture to a large serving bowl. Add the Parmesan and crushed red pepper, and toss to combine. Drizzle with the extra-virgin olive oil, and serve immediately.