Preheat the oven to 350°F and spray an 8 x 12-inch baking dish with cooking spray. Set aside. Prepare the cheese tortellini, per the package instructions slightly under cooking. [i.e. Cook for 7 minutes instead of 9] Drain well.
On the stovetop in a deep large skillet heat a couple of drizzles of olive oil. Add the diced onion. Cook for 2-3 minutes until the onion softens and is beginning to brown. Add the garlic and saute for 1 minute or until fragrant.
Add the ground beef and Italian sausage. Season with salt and black pepper to your taste. Cook until no pink remains then drain all excess fat from the pan.
Add marinara sauce. Stir until combined then remove from the heat.
Whip together the cream cheese, dry Italian seasoning and milk.
To assemble, Layer half of the cheese tortellini in the bottom of the baking dish. Top with ⅓ of the sauce.
Dollop ½ of the cream cheese in teaspoon portions randomly over the sauce, then cover with ½ of the shredded mozerella cheese.
Repeat, cheese tortellini, ⅓ sauce, the remaining cream cheese. Top with final ⅓ of sauce. Sprinkle reserved mozzarella cheese on top.
Bake for 30-40 minutes until bubbly and the cheese has browned.
Rest for 5-10 minutes, then serve.