Like cheesecakes, custard pies crack when they’re over-baked. The edges have finished cooking while the center hasn’t set: and when the pie shrinks as it cools, cracks can form. Prevent cracks by baking the pie at a moderate temperature, and–even better–bake custard pies in a water bath. This prevents the outer layer of custard from baking too fast. To avoid burns or dropped pies, only use heavy-duty aluminum, glass or ceramic pie pans: disposable foil pans are too shallow, are hard to grip, and can buckle when you try to remove them from a water bath. Use a rimmed baking sheet or glass baking pan big enough to hold the pie. Place the baked crust in the pan, add the custard, and carefully transfer the pan to the oven. Use a teakettle of hot water to pour in a depth of about half an inch; you can always add more water later, as it evaporates.
Remove the pie from the oven when the edges are set but the center still has a little “wiggle.” If the filling has started to puff up and soufflé, you’ve waited too long! If you’re using a water bath, take extra care. If your pie plate has handles or a deep rim, you can remove it from the water bath in the oven, leaving the water to cool before discarding. Otherwise, bring the whole pan out of the oven very slowly and steadily. Remove the pie from the water bath to cool on a rack.
Safety
Once the pie has cooled enough to hold the pan in your hands, transfer it from the counter to the fridge. Always store custard pies in the refrigerator: the eggs and milk in the custard can encourage bacterial growth that can be hazardous to your health.