I pour this luscious potato mixture into my prepared baking dish and spread it out into an even layer. Now, for the million-dollar finish: the topping. In a medium bowl (or the now-empty cereal bag), I combine the lightly crushed cornflakes with the remaining 1/4 cup of melted butter. I toss until every flake is gleaming and coated. Then, I sprinkle this buttery crunch evenly over the entire surface of the casserole, covering every inch. This layer is what bakes into that signature, irresistible crust.
The casserole goes into the preheated oven, and I cover it loosely with aluminum foil. This is my learned trick! I bake it covered for 25 minutes. This allows the casserole to heat through thoroughly and the flavors to meld without the topping burning. Then, I carefully remove the foil, turn the oven up to 400°F (200°C), and bake for another 15-20 minutes, uncovered, until the topping is deep golden brown and the edges are bubbly. The transformation is incredible. I pull it out and let it rest for 10 minutes before serving—this lets the sauce set just enough for perfect scooping.
Pro Tips for Best Results
For the most flavorful casserole, season the potato boiling water generously with salt, like you would for pasta. It’s your one chance to season the potatoes from the inside out. I didn’t do this the first time and found myself needing to overseason the sauce to compensate. Salting the water makes every bite perfectly seasoned.
To prevent a soggy topping, make sure your crushed cornflakes are lightly coated, not drowned, in butter. You want them to be moistened, not sitting in a pool. Also, ensure the casserole is hot and bubbly before you add the topping and put it in the oven. A cold base will steam the topping and make it soft.
Letting the casserole rest after baking is not a suggestion—it’s a rule. I learned this the hard way when I dug in immediately and the serving spoon brought up a delicious but soupy mess. Letting it sit for 10-15 minutes allows the starches in the potatoes and sauce to thicken everything up to the perfect scoopable consistency.
Common Mistakes to Avoid
The biggest mistake is overcooking the potatoes during the boiling stage. If they are mushy before they go into the casserole, they’ll completely disintegrate when mixed and baked, turning your dish into a gluey, homogenous mash. You want a defined cube that holds its shape. Test them early and often with a fork.
Don’t skip the foil tent for the first part of baking. I made this error, eager for a crispy top, and ended up with a beautifully bronzed crust over a still-cold center. The foil allows the interior to cook through gently before you crisp up the topping. It’s the key to a perfect bake from edge to edge.(See the next page below to continue…)