Mashed Potato Casserole is an easy and delicious way to use up leftover mashed potatoes from your holiday dinner. The leftover potatoes are layered in a casserole dish with cheese, cooked ham, and a crispy breadcrumb topping. It’s a great way to take those leftovers and turn them into a brand new dish.
Sometimes making the actual holiday dinner is the easy part. The hard part is knowing what to do with all the leftovers! Yes, you can just reheat them but turning them into something new is always better and this leftover mashed potato casserole is a great way to do it.
We always end up with lots of mashed potatoes for the holiday meal – everyone thinks they can eat twice what they really can! Sometimes our eyes are bigger than our stomachs, so this easy potato bake is the perfect way to use them all up. Once you add a few ingredients plus a crispy topping, those leftovers turn into a brand new meal.
What I love about this recipe is that you can easily adjust it based on what you have. So, you can swap the cooked ham for leftover Thanksgiving turkey or change the cheese to whatever you have in your fridge. It’s a flexible and easy side dish or main dish which is just what we all need after a big holiday celebration.
- Freshly grated parmesan cheese for the topping and filling
- Bread crumbs
- Plain leftover mashed potatoes
- All-purpose flour
- Salt and black pepper
- Large egg
- Cooked ham or speck cut into cubes – if you use prosciutto you may want to use a little less salt.
- Shredded Fontina or Gruyere cheese, be sure to shred your own cheese from a block, packaged shredded cheese always contains additives which can effect how the cheese melts and taste.
- Butter – melted and cooled, I use salted butter. If you use unsalted you should add another 1/4 teaspoon of salt.
Mix Parmesan cheese and breadcrumbs in a small bowl and set it aside. In a large bowl, combine the mashed potatoes, flour, Parmesan, salt, pepper, and egg.
Spread half of the mashed potato mixture in the prepared casserole dish. Sprinkle the cubed ham over the top.
Followed by the shredded cheese. Drop spoonfuls of the remaining potatoes on top of the cheese.
Then sprinkle the breadcrumb mixture over the top. Drop dots of butter on top of the breadcrumbs.
Bake the potato casserole for 35 to 45 minutes or until the top is golden brown. Let it sit at room temperature for five to ten minutes before serving.
Mashed Potatoes: We keep our potatoes pretty plain, but any kind of leftover mashed potatoes – like ones made with sour cream, butter, cream, and other add-ins like herbs and cheese – will work. If yours are very cheesy and rich, you might want to cut back on the added cheese for the casserole.
Meat: I love cooked ham in this dish, but leftover cubed turkey or roast chicken is wonderful, too. Cooked and crumbled bacon or pancetta would be great, also.
Cheese: Instead of Gruyere or Fontina cheese, try shredded sharp cheddar cheese, provolone, or Swiss cheese, or any other good melting cheese for a different flavor.
Garnishes: Feel free to top the baked casserole with sliced green onions, scallions, chives, or fresh chopped parsley for garnish.
Store leftovers in a sealed container in the refrigerator for up to 4 days. Reheat covered in the oven until heated through or in the microwave.
Be sure to cool the casserole completely in the baking dish, then cover it with plastic wrap and again with foil. It will keep in the freezer for up to 1 month. Thaw overnight in the refrigerator. Bake in a low oven until warmed through.
Yes it can be made ahead, be sure to cover the unbaked casserole and refrigerate, it will keep for up to 24 hours in the fridge.
The most common potato used are Russets, however Yukon Gold and red potatoes can also be used.
You might want to double the number of potatoes you mash this year just so you have enough to make this leftover mashed potato recipe the next day! It’s a cozy and satisfying dish – Enjoy!
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Leftover Mashed Potato Casserole
- 1-2 tablespoons freshly grated parmesan cheese
- 1-2 tablespoons bread crumbs
- 3 cups mashed potatoes*
- ⅓ cup all purpose flour
- ⅓ cup freshly grated parmesan cheese
- ½ teaspoon salt
- 2 dashes black pepper
- 1 large egg
- ¾ cup cubed cooked ham or speck (100 – 150 grams)
- 1 cup shredded Fontina/Gruyere
- 1-2 tablespoons butter
*It's best to use mashed potatoes that haven't been dressed but those would work also.
- Pre-heat oven to 350F (180C). Lightly grease and flour a medium 8 ½ x 4½ inch (21 x 11 cm) baking dish.
- In a small bowl mix together the parmesan cheese and bread crumbs. Set aside.
- In a large bowl add the mashed potatoes, flour, parmesan cheese, salt, pepper and egg. Mix to combine.
- Transfer ⅔ of the mixture to the prepared baking dish, and spread it evenly on the bottom and up half the sides of the pan.
- Sprinkle the cubed ham or speck on top, top with the shredded cheese, top with small spoonfuls of the remaining mashed potato mixture on top. Sprinkle the bread crumb mixture on top and dot with butter. Bake in the pre-heated oven for 35-45 minutes or until browned on top. Let sit 5-10 minutes before serving. Enjoy!