Prep the Potatoes: Thinly slice the potatoes, about ⅛-inch thick, and immediately plunge them into water. This helps to keep them from going brown while you prep everything else.
Heat Up: Preheat your oven to a cozy 350°F (177°C). Lightly grease a 9x13-inch baking dish and set it aside for now.
Meaty Matters: In a sizable 4-5 quart saucepan or Dutch oven, brown the ground beef, diced onions, and garlic over medium-high heat. Frequently stir and crumble the beef. Drain off any excess oil.
Sauce Time: In a separate bowl, mix together the cream of mushroom soup, half and half, onion powder, kosher salt, and freshly cracked black pepper. Stir until it’s all one big happy family.
Layer Up: Drain your potato slices. Place a third in the bottom of the baking dish. Top with a third of the meaty mix and ¾ cup shredded cheese. Drizzle a third of the creamy sauce over it.
More Layers: You're not done! Repeat with another layer of potatoes, meat, cheese, and sauce.
Final Touches: Add a last layer of potatoes and meat. Douse with the remaining sauce and crown with 1½ cups of shredded cheese.
Bake It: Cover the dish tightly with foil and bake for about 1 hour and 10 minutes. Then, unveil and bake for another 20 minutes.
Cool Off: Let it rest for 15 minutes before serving. Seriously, it's lava hot!
