Despite its name, this “omelet” is nothing like the filling-stuffed egg dish you expect at brunch, nor does it take a day to bake. This cheesy, golden, puffed casserole is all about the eggs, consisting of a rich custard, bread and cheese and yielding a melt-in-your-mouth texture that rivals even the fluffiest scrambled eggs.

The eggs, not the bread, should be this dish’s focus, so to keep their flavor at the fore, we prepared a milk-based custard. Buttered white bread, cut into bite-size pieces and layered with tangy cheddar cheese in a baking dish, promised to melt right into the custard while also bringing in plenty of richness.

A small amount of grated onion and a bit of dry mustard and hot sauce added just enough complexity to the creamy eggs. Refrigerating the assembled omelet overnight melded the flavors and saturated the bread, so all we had to do before brunch was bake it.

Cheesy and golden, this humble casserole puffed impressively above the rim of the baking dish, making it a tempting but unfussy centerpiece. Use the large holes of a box grater to grate the onion.

The omelet needs to sit in the refrigerator, well covered, for at least eight hours to achieve the desired consistency.