Preheat oven and prepare baking dish
Preheat oven to 350°F (175°C). Lightly grease a 9×13-inch casserole dish.

Cook the spaghetti
Bring a large pot of salted water to a boil. Cook spaghetti according to package directions until al dente. Drain and set aside.

Brown the beef
In a large skillet over medium heat, cook the ground beef until browned and fully cooked. Drain excess grease. Add garlic, Italian seasoning, and spaghetti sauce. Simmer for 5–7 minutes.

Mix pasta and cream cheese
While the sauce simmers, mix the softened cream cheese, garlic salt, and drained spaghetti together in a large bowl until pasta is evenly coated.

Layer the casserole
Spread the cream cheese-coated spaghetti into the prepared baking dish. Top with the meat sauce. Sprinkle Parmesan and mozzarella evenly over the top.

Bake
Bake uncovered for 25–30 minutes, or until cheese is melted and bubbly. For a golden top, broil the last 2 minutes.

Serve and enjoy
Let sit for 5 minutes before serving. Garnish with fresh basil or parsley if desired.