Step 1

Preheat Oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or butter.

Step 2

Make Meat Mixture: In a large skillet, cook the ground beef over medium heat until it's browned and no longer pink. Drain ALL excess fat from the skillet. This is a crucial step in the process so the casserole doesn't become greasy. Add the chopped onion and minced garlic to the skillet with the ground beef. Cook for an additional 2-3 minutes until the onion is softened. Stir in the Worcestershire sauce, garlic powder, onion powder, and paprika. Remove from heat and set aside.

Step 3

Make Roux: In a separate saucepan, melt the butter over medium heat. Whisk in the gluten-free all-purpose flour and cook for 1-2 minutes until it forms a smooth paste (roux). Gradually whisk in the milk, and beef broth until the sauce is smooth and thickened. Remove from heat and whisk in the Greek yogurt. Season with salt and pepper to taste. See notes for an substitute for homemade roux.

Step 4

Build Casserole: Arrange half of the sliced potatoes in an even layer on the bottom of the prepared baking dish. Spread half of the cooked ground beef mixture over the layer of potatoes. Pour half the cream sauce over the ground beef layer, spreading it evenly. Repeat the layers with the remaining potatoes, ground beef, and cream sauce

Step 5

Add Cheese & Bake: Sprinkle the mozzarella cheese and sharp cheddar cheese over the top of the casserole. Cover the baking dish with aluminum foil and bake in the oven for about 45-50 minutes, or until the potatoes are tender. Remove the foil and return the casserole to the oven for an additional 10-15 minutes, or until the cheese is melted and bubbly.