Things You'll Need
Ovenproof casserole or baking dishes
Plastic cling wrap
Heavy-duty freezer bags or aluminum foil (optional)
As with other hearty casseroles, shepherd's pie provides both a warmly comforting meal for immediate consumption at the table and a fine candidate for the freezer. You assemble the pie from already cooked ingredients, so you can make it up deliberately for later use, or portion leftovers and freeze them after serving the initial meal. The only major difference is that shepherd's pie frozen before baking won't have the signature golden crust, so plan to reheat it in the oven rather than a microwave.
Unbaked Shepherd's Pie
Prepare the meat filling according to your favorite recipe, then set it aside to cool while you boil your potatoes. When the potatoes are ready, mash them and season them to taste with salt and pepper, then enrich them with milk and butter if you wish.
Spread the meat filling in one large ovenproof casserole or baking dish, or divide it evenly between smaller dishes for individual meals. Cover the filling with an even layer of the mashed potatoes. Don't fluff or pattern the potatoes as you would if you were baking the dish immediately, since this creates air pockets that will shorten the pie's storage life.
Wrap each dish in plastic cling wrap, pressing the wrap directly to the surface of the potatoes and eliminating as much air as possible. For improved storage life, place each dish in a heavy-duty freezer bag or overwrap it with heavy-duty aluminum foil. Label the dish or dishes with the date.
Transfer the sealed casserole to your freezer, ensuring there's good airflow around it to speed cooling. If you've prepared multiple small pies, distribute them around the freezer in a single layer. If they're stacked, they won't cool as quickly.
Bake and eat the shepherd's pie within two to three months. After that time it will remain edible, but its flavor and quality will begin to diminish.
Leftover Shepherd's Pie
Prepare and bake the shepherd's pie as you normally would. When you've finished serving the meal, set your casserole dish in a well-ventilated location to cool.
Transfer the leftover portion of the pie to a smaller casserole dish, or divide it between several smaller containers for individual portions. Choose either oven-safe or microwave-safe containers, depending on your preferred reheating method.
Press a small sheet of plastic film wrap to the surface of each portion, to exclude as much air as possible, then seal microwaveable containers with their own airtight lids. If you're using open, oven-safe containers, wrap each portion in plastic film wrap individually. For better storage life, bag each portion in its own freezer bag or wrap it in foil.
Distribute the individual pies evenly throughout your freezer, so they'll cool quickly.
If you're preparing shepherd's pie specifically for the freezer, add one or more beaten eggs to the mashed potatoes. These help bind the moisture in the potatoes, improving the texture when the dish is baked. Thickening the gravy with potato starch, rather than flour or cornstarch, can help improve the texture of the filling after it's reheated.
If your leftover shepherd's pie is still warm, or if you have more than two or three portions, reduce the strain on your freezer by dividing the batch into halves. Freeze half of the portions immediately and leave the other half in your refrigerator to freeze the next day. This speeds freezing and minimizes the risk of damage to your already-frozen foods.
Cooks in the U.K. draw a distinction between "shepherd's" pie, which is made with lamb, and "cottage" pie, which is made with beef. In either case, they're usually made with diced leftover roast meats and gravy rather than uncooked ground meat.
If you freeze your shepherd's pie in a ceramic or glass casserole, don't place it directly into a preheated oven. Thermal shock might cause it to crack or explode, which at best wastes food and at worst can cause serious injury. Instead, thaw the casserole overnight in your fridge or place it in a cold oven and bring the oven up to temperature.