Step-by-Step Instructions
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Prep the Potatoes: Slice your potatoes thinly and uniformly. Keep them in a bowl of cold water while you prepare the sauce to prevent browning, then pat them dry.
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Make the Cheese Sauce: In a saucepan, melt butter and sauté the onions until soft. Whisk in flour to create a roux, then slowly add the milk and cream, whisking constantly until thickened. Remove from heat and stir in 2/3 of your shredded cheddar until melted.
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Layering: Lightly grease your baking dish. Arrange a layer of potatoes, overlapping them slightly. Pour a portion of the cheese sauce over the top. Repeat the layers until the dish is full.
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First Bake: Cover the dish tightly with foil. Bake at 190°C (375°F) for about 45 minutes. This steams the potatoes until they are tender.
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The Topping: Remove the foil and sprinkle the remaining cheddar cheese (and a bit of Parmesan if you like) over the top.
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The Final Crisp: Bake uncovered for another 15–20 minutes until the cheese is bubbling and has developed those deep golden-brown spots seen in your photo.
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The Rest: Let the dish sit for 10 minutes before serving. This is crucial as it allows the sauce to set so it doesn’t run when you scoop it.
Frequently Asked Questions (FAQ)
Q: My sauce looks curdled. What happened? A: This usually happens if the oven is too hot or if you used low-fat milk. Stick to whole milk and cream for the best stability.
Q: Can I make this ahead of time? A: Yes! You can assemble the dish a day in advance and keep it in the fridge. Just add an extra 10–15 minutes to the initial covered baking time.
Storage Tips
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Refrigeration: Store leftovers in an airtight container for up to 4 days.
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Reheating: These reheat beautifully in the oven at 150°C (300°F) to maintain the texture, though a microwave works well for a quick lunch.
Variations
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Smoky Au Gratin: Use smoked cheddar or add a teaspoon of smoked paprika to the sauce.
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Add Greens: Layer in some sautéed spinach or leeks between the potato layers for a nutritional boost.
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Herb Infused: Add fresh thyme or rosemary to the milk as it heats up for an earthy, aromatic twist.
How to Serve
Serve this in the baking dish to show off that beautiful crust. Garnish with a sprinkle of fresh chopped parsley (as seen in the image) for a pop of color. It is the perfect partner for a Sunday roast or as the centerpiece of a holiday meal.
