**Cook the Ground Beef**
Preheat your oven to 350°F (175°C). In a large skillet, cook the ground beef over medium-high heat, breaking it apart with a spoon, until browned and cooked through, about 5-7 minutes. Drain any excess fat and add the diced onion and minced garlic. Cook for an additional 2-3 minutes, until the onion becomes soft and translucent. Season with salt, pepper, oregano, and paprika. Remove from heat and set aside.
**Prepare the Creamy Sauce**
In a medium bowl, combine the sour cream, milk, and 1/2 cup of shredded cheddar cheese. Stir until smooth. Season with a pinch of salt and pepper.
**Assemble the Casserole**
In a greased 9x13-inch baking dish, layer the sliced potatoes evenly on the bottom. Spread half of the cooked ground beef mixture over the potatoes, followed by half of the creamy sauce. Repeat the layers, ending with a layer of the remaining creamy sauce on top.
**Bake the Casserole**
Cover the baking dish with aluminum foil and bake in the preheated oven for 40 minutes. Remove the foil and sprinkle the remaining 1/2 cup of shredded cheddar cheese on top. If desired, sprinkle breadcrumbs on top for added crunch. Return to the oven and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly, and the potatoes are tender.
**Serve**
Allow the casserole to cool for 5-10 minutes before serving. Slice into squares and enjoy!