01 -
Heat the oven to 400°F. Lightly grease a 9x13-inch baking dish.
02 -
Cook the ground beef and onion in a large skillet over medium-high heat for 7-9 minutes, breaking up the meat, until the beef is browned and the onion is soft. Drain excess grease.
03 -
Stir in the garlic, salt, pepper, cheddar cheese soup, cream of mushroom soup, milk, ketchup, and mustard. Cook for 1-2 minutes until smooth and hot.
04 -
Spread the beef mixture evenly in the prepared dish. Sprinkle with 1 cup of cheddar, then arrange the frozen fries over the top in a mostly single layer. Season the fries lightly with salt.
05 -
Bake for 30-35 minutes, until the edges are bubbling and the fries are hot and starting to crisp.
06 -
Sprinkle the remaining 1 cup cheddar over the fries. Bake 4-5 minutes more until melted. Broil for 1-2 minutes if you want a browner top, watching closely.
07 -
Let the casserole rest for 5 minutes. Top with green onions or parsley if using, then serve hot.