Preheat the oven to 375°F and grease a 13x9-inch baking dish.
In a small saucepan, whisk together the cheddar cheese soup and milk and heat until steaming. You can also add the mixture to a microwave safe dish and microwave on high heat for 3 minutes.
Remove the soup from heat and stir in 2 teaspoons minced garlic, ½ teaspoon onion powder, ¼ teaspoon black pepper, and ½ cup shredded cheddar cheese. Set aside.
In a small bowl, mix the Kosher salt, ground pepper, garlic powder, and onion powder. Set aside.
Arrange half of the sliced potatoes in the baking dish in an overlapping shingle pattern.
Sprinkle the potatoes with half of the seasoning mix and pour half of the cheese sauce over the top.
Layer the remaining potatoes into the baking dish, sprinkle with the spices, and pour on the remaining cheese sauce.
Cover the baking dish with foil and bake for 30–35 minutes, until bubbling around the edges (potatoes won’t be fully cooked yet).
Remove the pan from the oven and increase the temperature to 425°F.
Take off the foil and sprinkle the remaining shredded cheddar cheese over the top.
Return the baking dish to the oven and bake uncovered for 20–30 minutes, until the cheese is golden brown and the potatoes are fork-tender.
Let the dish sit for 10 minutes before serving to allow the sauce to thicken. Serve warm and enjoy!