Step 1: Preheat oven to 375°F and grease a 9×13 inch baking dish.
Step 2: Cook ziti according to package directions until al dente, then drain and set aside.
Step 3: In a large skillet, brown ground sausage over medium heat until fully cooked, about 8-10 minutes.
Step 4: Drain excess fat from sausage, then stir in marinara sauce and simmer for 5 minutes.
Step 5: In a medium bowl, mix ricotta, 1/2 cup Parmesan, egg, garlic, basil, salt, and pepper until well combined.
Step 6: Layer half the cooked ziti in the prepared baking dish, then spread all the ricotta mixture evenly over the pasta.
Step 7: Top with remaining ziti, then pour the sausage and sauce mixture over everything.
Step 8: Sprinkle remaining Parmesan and all mozzarella cheese evenly over the top.
Step 9: Cover with foil and bake for 20 minutes, then remove foil and bake for 10 more minutes until cheese is bubbly and golden.
Step 10: Let rest for 5 minutes, garnish with parsley, and serve hot.