Preheat oven to 375°F (190°C) and grease a 9×13-inch baking dish.

In a skillet over medium-high heat, cook ground beef and onions until beef is browned. Add garlic and cook for 1 more minute. Season with salt, pepper, and Italian seasoning. Drain excess grease.

In a bowl, mix cream of mushroom soup and milk until smooth. Layer half of the sliced potatoes in the baking dish. Top with half of the beef mixture and pour half of the soup mixture over it.

Repeat layers. Sprinkle shredded cheddar cheese evenly on top.

Cover with foil and bake for 40 minutes. Remove foil and bake for another 15-20 minutes until potatoes are tender and cheese is golden and bubbly.

Let cool for a few minutes before serving. Garnish with fresh thyme or parsley if desired.