Rinse escarole and tear into bite sized pieces.
Cook pasta in a large pot of salted water.
Reserve 1 cup water before draining.
While pasta water boils, heat a large non-stick skillet on medium heat.
Add olive oil; when hot add onions, peppers, garlic, salt and pepper.
Cook until soft, about 4-5 minutes.
Add sausage, breaking up with a wooden spoon and cook until golden, about 6 to 8 minutes.
Add escarole, cover and cook 2 minutes; remove the cover, stir and cook about 3 more minutes or until wilted.
Adjust salt and pepper to taste.
Add cooked pasta, red pepper flakes, reserved water and Parmigiano Reggiano, toss well and transfer to a large serving bowl.