01 -
Cut the Yukon gold potatoes into 1/8-inch thick slices and keep submerged in water to prevent discoloration.
02 -
Set oven to 350°F. Lightly coat a 9x13-inch baking dish with nonstick spray and reserve.
03 -
Sauté ground beef, diced onions, and minced garlic in a large saucepan over medium-high heat until the meat is well browned, breaking apart clumps as it cooks. Drain any rendered fat.
04 -
Combine cream of mushroom soup, half and half, onion powder, kosher salt, and black pepper in a medium bowl, whisking until completely smooth.
05 -
Drain the potato slices and layer one-third of them evenly in the prepared baking dish. Spread one-third of the beef mixture over the potatoes, then sprinkle with 3/4 cup shredded Colby Jack cheese and pour over one-third of the soup mixture.
06 -
Repeat layering process with another one-third of the potatoes, beef mixture, 3/4 cup cheese, and one-third of the soup mixture.
07 -
Arrange remaining potatoes and beef mixture as the top layer. Pour all remaining soup mixture evenly over the top and finish with the remaining 1.5 cups of shredded Colby Jack cheese.
08 -
Cover the dish tightly with aluminum foil and bake for 1 hour and 10 minutes.
09 -
Remove the foil and continue baking for an additional 20 minutes until bubbling and the top is golden.
10 -
Remove from oven and let the casserole stand for 15 minutes to set before portioning for service.