Bring a large pot of salted water to a boil. Add 1 pound of ziti pasta and cook according to package instructions until al dente. Drain the pasta and set aside.
In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add 1 diced onion and sauté for about 5 minutes until softened. Stir in 3 minced garlic cloves and cook for 1 more minute until fragrant.
Add 1 pound ground beef or turkey to the skillet. Cook until browned and no longer pink, breaking it apart with a spatula as it cooks. Season with salt and pepper.
Pour in 1 jar (24 ounces) of marinara sauce. Stir to combine and let simmer for 10 minutes on low heat, allowing the flavors to meld.
In a medium bowl, combine 15 ounces ricotta cheese, 1 egg, 1 teaspoon Italian seasoning, and a pinch of salt and pepper. Stir until smooth and well blended.
Preheat your oven to 375°F (190°C). In a large mixing bowl, combine the cooked ziti pasta with the meat sauce. Gently fold in the ricotta mixture, ensuring the pasta is evenly coated.
Transfer half of the pasta mixture into a greased 9x13-inch baking dish. Sprinkle 1 cup of shredded mozzarella evenly over the layer.
Add the remaining pasta mixture on top and finish with the remaining 1 cup mozzarella and 1/2 cup grated Parmesan cheese.
Cover the casserole loosely with foil and bake for 25 minutes. Remove the foil and bake for an additional 15 minutes or until the cheese is golden and bubbly.
Once out of the oven, let the baked ziti rest for 5 to 10 minutes. Garnish with fresh basil leaves before slicing and serving.