Spoon the burger sauce on top of the beef layer and smooth it with a spatula.
Sprinkle evenly with cheddar cheese (and mozzarella if using).
Arrange the frozen French fries in a single, even layer on top of the cheese.
Step 4: Bake
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Place in a preheated 400°F (200°C) oven and bake for 30–35 minutes, or until fries are golden and crisp and cheese is bubbling.
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For an extra crisp finish, broil for 2–3 minutes at the end — watch closely to prevent burning.
Step 5: Garnish and Serve
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Let the casserole rest for 5–10 minutes to allow layers to settle.
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Top with optional garnishes like diced tomatoes, shredded lettuce, green onions, or sesame seeds for that “burger with the works” feel.
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Serve hot — slices hold together better after resting.
