Get the oven ready and prep your dish. Preheat your oven to 180°C (350°F) and grease a 9x13 inch baking dish with a little butter. You want the oven fully up to temperature so the casserole starts cooking the moment it goes in.

Sweat the onions until they are sweet and translucent. In a large frying pan, melt 3 tablespoons of butter over a medium-low heat. Add the diced onion and cook for 8–10 minutes, stirring occasionally. You are looking for them to become soft and glassy, with a sweet, nutty aroma filling the pan. They should not take on any colour — just gentle, slow cooking.

Build the creamy, cheesy base. In a very large mixing bowl, combine the tin of condensed soup, the soured cream, 350g of grated cheddar, the garlic powder, white pepper, and smoked paprika. Stir until it forms a thick, pale-yellow mixture. Taste it — it should be creamy and well-seasoned, with a little tang from the soured cream.

Bring the hash browns into the fold. Add the thawed hash browns and the cooked onions to the bowl. Using a sturdy spatula, fold everything together until every shred of potato is coated in that wonderful, creamy sauce. The mixture will look thick and chunky, with the cheese clinging to the potatoes.

Transfer to the dish and create that signature top. Spoon the mixture into your prepared baking dish and spread it into an even layer. Sprinkle the extra handful of grated cheddar over the top — this will create a molten layer beneath the crisp topping.

Make the crunchy cornflake crown. In a small bowl, gently toss the crushed cornflakes with the 60g of melted butter until every flake is glistening. Sprinkle this buttery mixture evenly over the cheese layer. Do not press it down; you want it to sit loosely on top.

Bake until golden and bubbling. Place the dish in the preheated oven and bake for 45–50 minutes. You will know it is ready when the top is a deep, toasty golden brown and the filling is bubbling up around the edges with a soft, hissing sound. The kitchen will smell of toasted butter and cheese.

Rest before serving (the hardest step). Remove the dish from the oven and let it sit on the counter for at least 10 minutes. This rest time is crucial — it allows the sauce to thicken and set so you get neat, glorious slices rather than a soupy mess. After testing this recipe five times, I finally got it just right, and the rest is the secret to that perfect slice.