Remove sausage from casings and cook over medium-high heat in a sauce pot sprayed with non-stick spray. Brown 8-9 minutes; remove from pan and set aside.
Add onion and garlic to the pan with a good pinch of salt and pepper and saute until softened, about 5-7 minutes.
Meanwhile, mix together ricotta, egg and parsley in a small bowl; set aside.
Add eggplant to the onion mixture with another pinch of salt and pepper stirring frequently until softened, about 6-7 minutes.
Add tomato basil sauce to the pan along with cooked sausage and pasta. Check for seasoning and adjust accordingly; remove from heat.
Pour 1/3 of the pasta/sausage mixture into a 9 x 13 baking pan then top with half of the ricotta mixture using a tablespoon to create big dollops. Add another 1/3 of the pasta mixture and top with the remaining half of the ricotta. Finally, add the remaining pasta then sprinkle parmesan cheese evenly on top.
Cover with foil and bake for 45 minutes.
Turn broiler on high for the last few minutes to create a bubbly, cheesey, delicious topping.
Notes
When browning sausage, don't be afraid of a little color. The browner, the better, because brown = flavor!