Step 1: Preheat Your Oven

• Preheat your oven to 350°F (175°C).

Step 2: Cook the Ground Beef

• In a large skillet, cook the ground beef over medium heat until it’s browned. Drain any excess fat.
• Add the diced onion and minced garlic to the skillet. Cook until the onion is translucent and the garlic is fragrant.

Step 3: Prepare the Sauce

• In a medium saucepan, melt the butter over medium heat.
• Stir in the flour to make a roux, cooking for about 1 minute.
• Gradually whisk in the beef broth and milk, stirring constantly until the mixture thickens.
• Add the cream of mushroom soup, salt, pepper, paprika, and dried thyme. Stir to combine.

Step 4: Assemble the Casserole

• In a greased 9×13-inch baking dish, layer half of the sliced potatoes.
• Spread half of the ground beef mixture over the potatoes.
• Pour half of the sauce over the beef and potatoes.
• Sprinkle with half of the cheddar and mozzarella cheeses.
• Repeat the layers with the remaining potatoes, ground beef mixture, sauce, and cheeses.

Step 5: Bake the Casserole

• Cover the baking dish with aluminum foil and bake in the preheated oven for 60 minutes.
• Remove the foil and bake for an additional 15-20 minutes, or until the potatoes are tender and the cheese is golden and bubbly.

Step 6: Garnish and Serve

• Let the casserole cool for a few minutes before serving.
• Garnish with chopped fresh parsley, if desired.