01 - Set the oven temperature to 375°F.
02 - Warm olive oil in a large skillet over medium heat. Add chopped onions and minced garlic, cooking until translucent, about 3 minutes.
03 - Incorporate the ground beef, breaking it apart with a spoon. Cook until browned, approximately 6 to 8 minutes. Drain excess fat.
04 - Sprinkle flour over the beef mixture and stir continuously for 1 minute to cook the flour.
05 - Gradually pour in beef broth while stirring to prevent lumps. Simmer for 3 to 4 minutes until slightly thickened. Season with thyme, oregano, paprika, salt, and pepper. Remove from heat.
06 - Grease a 9x13 inch baking dish. Arrange half of the sliced potatoes evenly across the bottom.
07 - Spread half of the prepared beef mixture over the potato layer. Repeat with remaining potatoes and beef mixture in alternating layers.
08 - Pour the whole milk evenly over the layered ingredients. Cover the dish tightly with aluminum foil.
09 - Place the casserole in the oven and bake for 50 minutes covered.
10 - Remove the foil, sprinkle shredded cheddar on top, and continue baking uncovered for 20 minutes until the cheese melts and starts to brown, and potatoes are tender.
11 - Allow the dish to stand for 10 minutes to set before serving.