Prep the slow cooker: Lightly grease the inside of your crockpot with cooking spray or a thin layer of butter to prevent sticking.

Brown the beef: In a skillet over medium-high heat, add oil and cook the ground beef until browned and crumbled, about 6–8 minutes. Season with a pinch of salt and pepper. Drain excess fat.

Slice the vegetables: Thinly slice the potatoes (about 1/8–1/4 inch) and onion. Uniform slices help the casserole cook evenly.

Mix the sauce: In a bowl, whisk together cream of mushroom soup, cream of chicken soup, milk or broth, garlic powder, onion powder, paprika, and Italian seasoning. Taste and adjust salt and pepper.

Layer the ingredients: Place half the sliced potatoes in an even layer in the crockpot, followed by half the onion, half the cooked beef, and one-third of the cheese. Pour over half the sauce. Repeat with the remaining potatoes, onion, beef, another third of the cheese, and the rest of the sauce. Reserve the last third of the cheese for later.

Cook: Cover and cook on Low for 6–7 hours or High for 3–4 hours, until the potatoes are tender when pierced with a fork.

Add the final cheese: In the last 15 minutes of cooking, sprinkle the remaining cheese on top. Cover just until melted and gooey.

Rest and serve: Turn off the heat and let the casserole rest for 10 minutes. This helps it set. Garnish with chopped parsley or chives.