Preheat the oven to 375 degrees F (190 degrees C). Lightly coat an 8-inch square baking dish with cooking spray.

Heat a large nonstick skillet over medium-high heat. Add turkey and onion; cook and stir until turkey browned and crumbly and onion soft, about 10 minutes. Drain.

Fill a large pot of lightly salted water and bring to a rapid boil. Cook egg noodles at a boil, stirring occasionally, until tender yet firm to the bite, about 5 minutes. Drain and return to the pot.

While the water is coming to a boil, stir tomato sauce and Italian seasoning into turkey mixture; bring to a boil over medium heat. Reduce heat to low and cover; simmer for 10 minutes.

Meanwhile, combine milk, cream cheese, parsley, and garlic in a small saucepan over medium heat; cook and stir until cream cheese melts, about 5 minutes. Pour over egg noodles; stir to combine. Transfer to the prepared baking dish.

Layer turkey mixture over noodles; sprinkle mozzarella cheese on top.

Bake in the preheated oven until casserole hot and cheese melted, 15 to 30 minutes.