Step 1

Preheat oven to 350 degrees F. Spray a 2-quart baking dish with cooking spray and set aside (I used an 11 x 7-inch dish, but a deep 8- or 9-inch square dish will also work).

Step 2

Cook spaghetti in a large pot of salted boiling water, just until cooked through but still firm to the bite (about 7-8 minutes). Drain.

Step 3

Meanwhile, in a large skillet, cook the beef, onion and garlic over medium heat until meat is no longer pink (about 6-8 minutes); drain. Stir in the spaghetti sauce, salt and pepper. Turn heat to low, and add cream cheese, sour cream and green onions; stir just until cream cheese is melted (about 2-3 minutes). Remove from heat, add the cooked pasta, and toss to combine.

Step 4

Transfer to prepared baking dish. Sprinkle mozzarella and Parmesan cheeses over top. Cover and bake for 25 minutes. Uncover; bake for 5 more minutes, or until casserole is bubbly.