Preheat oven to 400°F (200°C). Lightly grease a 9x13 inch baking dish.

In a large skillet, cook the ground beef and diced onion over medium-high heat until beef is browned. Drain excess grease. Stir in minced garlic and cook for 1 minute more.

In a separate saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Gradually whisk in milk and beef broth until smooth. Simmer for 3-4 minutes until thickened.

Remove sauce from heat. Stir in 1.5 cups of cheddar cheese, Worcestershire sauce, salt, pepper, paprika, and garlic powder until cheese is melted. Add the cooked beef mixture to the sauce and stir to combine.

Layer half of the sliced potatoes in the baking dish. Top with half of the beef/sauce mixture. Repeat with the remaining potatoes and beef mixture.

Cover tightly with foil and bake for 45 minutes. Remove foil, sprinkle with the remaining 1/2 cup of cheese, and bake uncovered for another 15-20 minutes until potatoes are tender and the top is bubbly and golden.

Let the casserole rest for 10-15 minutes before serving.