01 -
In a small saucepan, combine the sliced squash, chopped onion, and 1/4 teaspoon of salt. Cover with water and bring to a boil. Reduce the heat and simmer, uncovered, until the squash is crisp-tender, about 2 minutes. Drain the mixture well to remove excess water.
02 -
In a small bowl, whisk together the egg, mayonnaise, sugar, pepper, and the remaining 1/4 teaspoon of salt until well blended. Stir in the shredded cheddar cheese and the cooked squash mixture.
03 -
Preheat your oven to 350°F (175°C). Transfer the squash mixture to a greased 2-cup baking dish. In a small bowl, toss the crushed cornflakes with the melted butter. Sprinkle the buttered cornflakes evenly over the top of the casserole.
04 -
Bake, uncovered, in the preheated oven until the top is golden brown and the casserole is bubbly, about 25-30 minutes. Allow the casserole to cool slightly before serving.