Step 1: Preheat the Oven

Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with cooking spray or butter.

Step 2: Prepare the Ground Beef

In a large skillet, heat a drizzle of olive oil over medium-high heat. Add the ground beef and cook, breaking it up with a spatula, until browned and cooked through, about 5–7 minutes. Add the chopped onion and garlic, cooking for an additional 2–3 minutes until fragrant. Season with salt and black pepper. Drain excess grease if necessary.

Step 3: Slice and Season the Potatoes

Wash and peel the potatoes (if desired), then slice them thinly using a sharp knife or mandoline. In a large bowl, toss the potato slices with olive oil, paprika, garlic powder, salt, and black pepper.

Step 4: Make the Creamy Sauce

In a medium bowl, whisk together the cream of mushroom soup, milk, sour cream, and thyme (if using). Mix until smooth and well combined.

Step 5: Assemble the Casserole

• Spread the cooked ground beef mixture evenly across the bottom of the prepared baking dish.
• Arrange the potato slices in overlapping layers on top of the ground beef.
• Pour the creamy sauce evenly over the potato layer, ensuring it coats all the slices.

Step 6: Add the Cheese Topping

Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes. Remove the foil, sprinkle the shredded cheddar cheese over the top, and bake for an additional 15 minutes, or until the cheese is melted and bubbly and the potatoes are tender.

Step 7: Cool and Serve

Allow the casserole to cool for 5–10 minutes before serving. Garnish with chopped parsley for a pop of color, if desired.