Ingredients
For the Beef Layer:
1 tablespoon olive oil
1 medium yellow onion, finely chopped
1½ pounds lean ground beef
3 garlic cloves, minced
1 teaspoon salt
½ teaspoon ground black pepper
1 teaspoon paprika
½ teaspoon garlic powder
½ teaspoon onion powder
1 tablespoon tomato paste
1 tablespoon Worcestershire sauce
For the Potatoes and Sauce:
2½ pounds russet or Yukon Gold potatoes
3 tablespoons unsalted butter
3 tablespoons all-purpose flour
2 cups whole milk
1 cup low-sodium beef broth
½ teaspoon salt
¼ teaspoon ground black pepper
½ teaspoon dried thyme
1½ cups shredded sharp cheddar cheese, divided
1 cup shredded mozzarella cheese
2 tablespoons chopped fresh parsley, optional
Cooking spray or butter, for greasing the baking dish
Instructions
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Preheat the oven to 375°F.
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Lightly grease a 9-by-13-inch baking dish with cooking spray or butter.
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Peel the potatoes, if desired, and cut them into slices about â…› inch thick.
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Place the potato slices in cold water while preparing the remaining ingredients.
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Heat the olive oil in a large skillet over medium heat.
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Add the chopped onion and cook for 3 to 4 minutes, until softened.
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Add the ground beef and break it into small crumbles.
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Cook for 6 to 8 minutes, or until the beef is browned and no pink remains.
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Drain any excess grease from the skillet.
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Add the garlic, salt, black pepper, paprika, garlic powder, onion powder, tomato paste, and Worcestershire sauce.
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Cook for 1 to 2 minutes, stirring frequently, then remove the skillet from the heat.
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Melt the butter in a medium saucepan over medium heat.
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Add the flour and whisk continuously for 1 minute.
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Slowly pour in the milk while whisking constantly.
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Add the beef broth, salt, black pepper, and dried thyme.
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Cook for 4 to 6 minutes, stirring often, until the sauce thickens enough to coat the back of a spoon.
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Remove the saucepan from the heat.
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Add ½ cup of shredded cheddar cheese and stir until melted and smooth.
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Drain the potato slices and pat them dry.
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Arrange half of the potato slices in the bottom of the prepared baking dish, slightly overlapping them.
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Spoon half of the seasoned beef evenly over the potatoes.
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Pour one-third of the cheese sauce over the beef.
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Arrange the remaining potato slices over the first layer.
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Add the remaining ground beef.
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Pour the remaining cheese sauce evenly over the casserole.
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Press the layers gently so the sauce settles between the potato slices.
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Cover the baking dish tightly with aluminum foil.
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Bake for 50 minutes.
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Remove the foil and sprinkle the remaining cheddar and all the mozzarella over the casserole.
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Bake uncovered for another 20 to 25 minutes, or until the potatoes are tender and the cheese is bubbling and golden.
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Let the casserole rest for 10 minutes before serving.
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Sprinkle with chopped parsley, if desired.
Notes
Slice the potatoes approximately â…› inch thick so they cook evenly and become tender.
A mandoline slicer makes it easier to create evenly sized potato slices.
Russet potatoes produce soft layers and absorb more sauce. Yukon Gold potatoes hold their shape better and have a buttery flavor.
Keep the casserole tightly covered during the first 50 minutes so the trapped steam can cook the potatoes.
If the potatoes are still firm, cover the dish again and bake for an additional 10 to 15 minutes.
Ground turkey or ground chicken can replace the ground beef.
Monterey Jack or Colby Jack can replace part of the cheddar cheese.
Cooked mushrooms, diced bell peppers, or peas can be added to the beef mixture.
The casserole can be assembled up to 24 hours ahead and refrigerated before baking.
A refrigerated casserole may require an additional 10 to 15 minutes of baking time.
Store leftovers in an airtight container in the refrigerator for up to 4 days.
Reheat individual portions in the microwave or cover and warm in a 350°F oven.
Add a small splash of milk before reheating if the sauce seems dry.
Freeze the baked and cooled casserole for up to 2 months.
Thaw overnight in the refrigerator before reheating.