Preheat oven to 350f degrees. Spray an 11x7 (2 1/2 quart) casserole dish with nonstick cooking spray. Note: If all you have is a 9x13 baking dish then just use that.
In a large skillet, brown and crumble ground beef, Italian sausage and onion over a medium heat. Season the mixture with salt and pepper. Once cooked, drain excess grease.
Meanwhile, steam the broccoli just until tender. You want the broccoli to stay just a bit crisp. Season broccoli with a bit of salt and pepper.
Place cream cheese in a microwave-safe bowl and microwave on HIGH for about 45 seconds, until soft. Stir until creamy. Gradually stir in the heavy cream. Finally, stir in the Parmesan cheese, oregano and garlic.
Combine cooked ground beef, Italian sausage, broccoli and cream sauce into prepared baking dish and stir together well. Taste test and add additional salt and pepper. Top with shredded mozzarella cheese.
Cover with nonstick aluminum foil.
Bake at 350f degrees for about 35-45 minutes. Cheese should be melted and the edges should be a very light golden-brown.