Step 5: Rest and Serve
Remove the casserole from the oven and allow it to rest, uncovered, for 10 to 15 minutes before serving. This resting time is not optional — it allows the sauce to thicken and set, and the casserole to firm up enough to serve in distinct portions rather than a runny pool. The dish will hold its heat well during this time. Sprinkle with fresh parsley before serving if desired, and serve directly from the baking dish with a large spoon.
The Details That Make the Difference
Potato thickness and uniformity matter more than any other single variable in this recipe. Slices that are too thick will remain firm and underdone in the center while the edges overcook; slices that are too thin will dissolve into the sauce. A consistent quarter-inch is the target. If your potatoes are still firm after the indicated baking time, cover the dish again with foil and return it to the oven in 15-minute increments until a knife slides through without resistance.
The chicken broth addition — one of the adjustments that distinguishes home cooks who have made this dish fifty times from those making it for the first time — contributes a savory, slightly acidic depth to the white sauce that pure milk cannot provide. It complements the saltiness of the ham and balances the richness of the butter and dairy in a way that makes the finished sauce taste considerably more complex than its straightforward ingredient list suggests.
Make-ahead preparation is fully supported and actually recommended: assemble the casserole completely, cover it with plastic wrap, and refrigerate overnight. Remove it from the refrigerator 30 to 60 minutes before baking to take the chill off, then bake as directed, adding 10 to 15 minutes to the covered baking time to account for the cold starting temperature.
Storage
Leftovers keep well refrigerated in an airtight container for three to four days. Reheat individual portions in the microwave covered with a damp paper towel, or reheat larger amounts covered with foil in a 325°F oven until warmed through. The casserole can be frozen after baking — allow it to cool completely, wrap tightly, and freeze for up to two months. Thaw overnight in the refrigerator before reheating. Do not freeze the uncooked assembled casserole, as the raw potatoes will turn grainy and watery after thawing.
