Boil water for pasta. Cook pasta al dente. 1 minute before it is done, cook the rapini for 30 seconds in the water.
Meanwhile, heat a large sauté pan with olive oil over medium-high heat. Add sausage and break it up with the back of a wooden spoon into bite size pieces. Remove from pan once it is browned and cooked through, keeping the oil in the pan.
Add the eggplant to the pan with 1 to 2 tablespoons more olive oil (eggplant absorbs a lot), and cook until it is soft, about 4 more minutes (reduce heat to medium).
Add garlic and pepper flakes, cook for another minute. Add the rapini and sausage back to the pan.
Add cream and bring to a simmer. Add the cooked pasta and cook for another few minutes until the sauce thickens and coats the pasta.
Remove from heat, stir in 1/2 to 3/4 cup grated parmesan. Season with salt & pepper.