Bring a large pot of salted water to boil for the pasta. Add the olive oil to a large skillet over medium heat. When the oil is hot, add the sausage. Break the meat up with a wooden spoon, and cook until it’s no longer pink, about five to six minutes.
Add the garlic and red pepper flakes, and let sizzle a minute. Add the chopped escarole, in batches if necessary, and season with salt. Cover the escarole, and let it wilt, about three to four minutes.
Meanwhile, add the pasta to the water. Once the escarole has wilted, uncover and add the chicken stock. Bring to a simmer, and cook until the escarole is tender and the sauce has reduced by half, about five minutes.
When the pasta is al dente, remove it with a spider and transfer directly to the sauce. Toss to coat the pasta with the sauce, adding a little pasta water if it seems dry.
Turn off the heat, and sprinkle with the grated cheese. Toss and serve.