Move over plain potato side dish and serve this delicious Mashed Potato Gratin! Creamy potatoes, mixed with cheese, and topped with a crispy, buttery panko topping.

Mashed Potato Gratin

When I think of mashed potatoes, I think of the standard side dish that everyone loves. The family favorite that is easier to make than other potato gratins and can be whipped up in a jiffy.

Sometimes you need to elevate them without getting too fancy or blowing out the budget.

This Mashed Potato Gratin is just what you are looking for!

Why this recipe is amazing!

You can make it ahead of time
The buttery crispy topping is delicious!
A great way to use up leftover mashed potatoes
Freezes beautifully!

labeled picture of mashed potato gratin ingredients

Ingredients Needed

Potatoes – Russets are the best potato for this. I use 5 large one or roughly 3 pounds.

Sour Cream – Feel free to use full fat, reduced fat, or low fat works. You can also use plain Greek yogurt.

Milk – I use 1% but you can also use fat free. Substitute half and half if you would like even creamier potatoes.

Cheese – I use Emmentaler (Swiss cheese) but you can use Gruyere, cheddar, or mozzarella

Egg – 1 large is best here. Bring it to room temperature before beating.

Looking for more leftover worthy dishes? Follow LTB on Pinterest and pin to a board!

diced potatoes in a pot — peel and cube potatoes

cooked potatoes in a pot — peel and cube potatoes

How to make Mashed Potato Gratin

First: Heat oven to 375F. Peel and dice the potatoes. Place in a large pot and cover with cold water. Add 2 teaspoons salt. Bring to boil over high heat and cook until the potatoes are fork tender. Drain and return potatoes to the pot.

mashed potatoes in a pot — add butter, milk, and sour cream

Second: Gently mash the potatoes. Add the milk, sour cream, cheese, and butter. Mix to combine. Season with salt and pepper as desired.

panko and butter in a bowl — mix panko and butter

unbaked mashed potato gratin — mix panko and butter

Third: Spray the baking dish with cooking spray to prevent sticking. Spread the potato mixture in the prepared baking dish. Top with panko bread crumbs.

Fourth: Bake at 375F for 20 minutes or until the top is golden brown. Remove from the oven and enjoy!

For the full recipe and detailed baking instructions, please see the recipe card at the end of this post.

casserole in a dish with a scoop missing

How to Store

LEFTOVERS: Store any leftover mashed potato gratin in the refrigerator, in an air tight container, for up to 4 days.

REHEAT: To reheat, place in a 350F oven for 15 to 20 minutes until heated through. If the potatoes start to get a little dry, add 1/2 cup of broth, water, or milk and stir. Then bake.

FREEZE: Prep and wrap tightly in plastic wrap. Freeze for up to 2 months. Thaw overnight in the refrigerator, top with panko, cover with foil and bake as directed.

Can I make this ahead of time?

Sure you can! Just prep and keep it covered and refrigerated until ready to bake. I think leaving off the panko crumbs until just ready to bake. This way they don’t get soggy.

Why are my mashed potatoes gluey or gummy?

The main reason that mashed potatoes get gluey or gummy is over processing. Be sure to cook the potatoes until they are fork tender.

When you mash them, I like to use a potato masher or a wide fork. Just mash until most of the large chunks are gone.

Adding in the rest of the ingredients, be sure to gently fold them in and do not over mix!

Tips for No Leftovers

Be sure to salt the water when cooking the potatoes so they get some extra seasoning!
Boil the potatoes in chicken broth for a richer flavor instead of plain water.
Choose your favorite cheese when mixing in.
Substitute 1 large egg for 2 egg yolks.
Use 1/2 cup of the potato water or warm milk when mashing the potatoes.
Mix the panko with 1 tablespoon of melted butter before sprinkling on top of the potato gratin. It will help them brown faster.
Switch up the cheese to your favorite to make this mashed potato gratin your own.

If you love this recipe as much as I do, please write a five-star review in the comment section below (or on Pinterest with the “tried it” button – you can now add pictures into reviews, too!), and be sure to help me share on facebook!

scoop of mashed potatoes with text "mashed potato gratin"

This creamy and fluffy Mashed Potato Gratin is perfect for using up leftover mashed potatoes, or make fresh, and is an elegant side dish for any occasion!