This is the ultimate cozy breakfast casserole. Simple ingredients transform into a rich, custardy bake with a crisp, buttery topping, all thanks to an overnight rest in the fridge. It's a stress-free solution for special weekends or feeding a crowd.
Stale or day-old bread works best. Do not skip the overnight soak, as it is essential for the creamy texture. For a blueberry version, toss 1 1/2 cups of fresh or frozen berries with the bread cubes before adding the custard.