Whether you've got a whole bread pudding in the freezer or a piece leftover in the fridge, when it comes to reheating there are two options: microwave or oven. In either situation, what's most important is warming the dessert without drying it out. You also have the option of eating it cold or at room temperature, however, it doesn't really compare to the rich, creamy flavor of warm bread pudding.
From the Refrigerator
Leftover bread pudding stays good in the fridge for about 3-4 days, but will start loosing moistness after 1-2 days. To reheat in the oven, preheat to 350 degrees Fahrenheit, cover the pudding with foil and cook for 5 to 15 minutes depending If you're using a microwave cook on low power for 2 to 10 minutes, checking it often. For either method, heat the pudding until it reaches a temperature of 165 F.
From the Freezer
Frozen bread pudding, baked ahead of time, will keep for 2 to 3 months in the freezer (cool the dish in the refrigerator before setting it in the freezer). When ready to eat, thaw the frozen pudding in the refrigerator overnight.Check that it's completely thawed by inserting a skewer or knife in the center of the dish. After thawing reheat frozen bread pudding either in the oven or microwave in the same way you would leftover bread pudding.
Storage and Reheating Tips
Because bread pudding can be dry to begin with, you need to store the dish in a way that prevents it from drying out further. If storing in the fridge, cover it tightly with plastic wrap or if in the freezer use a few layers of foil to minimize drying.
If you want a crisp top on your bread pudding, place it in an oven-safe dish under the broiler for 1 minute after reheating in either the oven or the microwave.
If all of the custard portion of the bread pudding has disappeared, it's safe to say it's dried out -- a result of the bread soaking up all the moisture. If this happens add sauce, ice cream, whipped cream or a splash of heavy cream just before serving the warmed dish. Sauces that work well in bread pudding include: caramel sauce, creme anglaise, or a custard sauce (make with 2 eggs , 1cup of cream or milk and a 1/4 cup of sugar).