Preheat oven to 425 degrees and line a baking sheet with aluminum foil. Place a large skillet over medium-high heat and add ground beef, salt and pepper. Brown the ground beef, breaking up into small pieces as it cooks until no pink remains. Drain excess grease.
Add onion and garlic to the beef and cook 3-4 minutes, stirring frequently. Add entire jar of pizza sauce and stir to combine. Bring liquid to a bubble then remove from heat, add cooked spaghetti noodles, stir to combine, and set aside.
Cut French bread in half lengthwise and spread the inside of each half with softened butter. Sprinkle the buttered area with garlic salt and place on baking sheet buttered side up. Bake the garlic bread for 8 minutes, until just beginning to brown around the edges.
Remove from oven and heap the spaghetti mixture onto each half of the garlic bread. Sprinkle top of spaghetti with shredded mozzarella and return to oven for 10 minutes, just until cheese is melted and bubbly, and everything is hot and crispy.
Remove from oven, sprinkle with chopped parsley and cut into large pieces. Enjoy!
Notes
If you're short on time, pre-buttered and seasoned garlic bread can be found in the deli section of the supermarket!