Make-Ahead Mashed Potato Casserole For Thanksgiving

When you are preparing a big holiday dinner, this Make-Ahead Mashed Potato Casserole is an easy way to get one important side dish finished before Thanksgiving Day. The potatoes stay creamy, bake beautifully and can be prepared up to two days ahead of time.

Mashed potatoes are one of those side dishes that everyone expects to see on the Thanksgiving table. However, making them at the last minute can be difficult. They take up room on the stove, require peeling and chopping, and somehow always seem to be ready before or after everything else.

That is why this casserole is so helpful. The potatoes are boiled, mashed and placed in a baking dish when you have time. Then, on the day of your dinner, all you have to do is place the dish in the oven.

Cream cheese, sour cream, butter and milk keep the potatoes soft and creamy as they bake. A little extra butter on top gives the casserole a lightly golden surface without turning it into a heavy or overly rich side dish.

Best of all, this recipe makes enough to serve a crowd. It is perfect for Thanksgiving, Christmas or any time you need a large amount of mashed potatoes without the last-minute work.

Make-Ahead Mashed Potato Casserole

This recipe begins with five pounds of potatoes. That may sound like a lot, but once the potatoes are peeled and cooked, it is the right amount for a standard 9 x 13-inch casserole dish.

You will get approximately 12 servings, depending on the number of other side dishes being offered. However, if mashed potatoes are especially popular with your family, plan on slightly larger portions.

For another easy way to prepare potatoes, try my Instant Pot mashed potatoes. However, when oven space is available, this make-ahead casserole is a better choice for getting the preparation finished before the holiday.

The Best Potatoes To Use

The type of potato you use has a big impact on the texture of mashed potatoes. For the best results, use Russet potatoes, Yukon Gold potatoes or a combination of both.

Russet potatoes contain more starch and produce light, fluffy mashed potatoes. They absorb butter and milk well, but they can become dry if there is not enough liquid in the recipe.

Yukon Gold potatoes are naturally creamy and have a slightly buttery flavor. Their texture is a little denser than Russet potatoes, but they hold up extremely well when the casserole is refrigerated and reheated.

I prefer to use half Russet potatoes and half Yukon Gold potatoes. This gives the casserole the fluffy texture of Russets along with the rich and creamy texture of Yukon Golds.

However, you can use all of one variety if that is what you have available.

Avoid using waxy red potatoes as the main potato in this casserole. They can be more difficult to mash smoothly and may develop a gluey texture if overworked.

Ingredients Needed

Potatoes

Peel the potatoes and cut them into pieces that are approximately the same size. Uniform pieces will finish cooking at the same time.

Although you can leave some of the skin on Yukon Gold potatoes for everyday mashed potatoes, I recommend peeling them for this holiday casserole. The finished dish will have a smoother and more traditional appearance.

Cream Cheese

Use one standard block of cream cheese. Let it soften at room temperature so it melts easily into the hot potatoes.

Cream cheese gives the potatoes body and helps prevent them from becoming watery. It also helps them maintain a creamy texture after being refrigerated.

Sour Cream

Sour cream adds moisture and a slight tang that balances the richness of the butter and cream cheese.

Full-fat sour cream provides the creamiest results. Light sour cream can be used, but avoid fat-free sour cream because it may release additional liquid as the casserole bakes.

Butter

Butter is mixed directly into the potatoes, and a smaller amount is reserved for the top. Use salted or unsalted butter and adjust the added salt accordingly.

Milk

Whole milk makes the potatoes creamy without making them too heavy. You can also use half-and-half for a richer casserole.

Warm the milk before adding it to the potatoes. Cold milk will cool the potatoes and will not absorb as easily.

Seasonings

Garlic powder, salt and black pepper provide simple flavor without competing with the rest of the Thanksgiving meal.

Taste the potatoes before transferring them to the baking dish. Potatoes require a fair amount of seasoning, especially when making a large batch.

How To Make Mashed Potato Casserole

Begin by peeling and cutting the potatoes into 1½ to 2-inch pieces. Place them in a large stockpot and cover them with cold water by approximately one inch.

Starting the potatoes in cold water allows the inside and outside of each piece to cook evenly. If they are placed directly into boiling water, the outside may soften before the center is cooked.

Add a generous pinch of salt to the water. Bring it to a boil over medium-high heat, then reduce the heat enough to maintain a gentle boil.

Cook the potatoes until they are fork-tender. Depending on the size of the pieces, this will take approximately 15 to 20 minutes.

A fork should slide easily into the center without the potato falling apart in the water.

Drain The Potatoes Well

Drain the cooked potatoes in a large colander. Let them sit for two or three minutes so excess steam can escape.

This step is important because water left on the potatoes can make the casserole loose or watery.

Return the drained potatoes to the warm pot and place it over low heat for approximately one minute. Gently move the potatoes around to allow any remaining moisture to evaporate.

Remove the pot from the heat before adding the remaining ingredients.

How To Keep The Potatoes Creamy

Add the softened cream cheese, sour cream and butter while the potatoes are still hot. Mash until the large pieces are gone.

Gradually add the warm milk, using only as much as needed. The potatoes should be slightly softer than you would normally serve them because they will firm up after being refrigerated and baked.

Do not add all the milk at once. The exact amount needed will depend on the variety and moisture content of the potatoes.

Season with garlic powder, salt and pepper. Taste and adjust the seasonings before placing the mixture in the casserole dish.

Try not to overmix the potatoes. Excessive mixing releases too much starch and can make them sticky. A standard potato masher works well, although a potato ricer makes for an especially smooth consistency.

As tempted as you may be, avoid using a food processor or blender. It's simply too easy to overwork the potatoes.

Preparing The Mashed Potato Casserole

Grease a 9 x 13-inch baking dish with butter or nonstick cooking spray. Spoon the mashed potatoes into the dish and spread them into an even layer.

Use the back of a spoon to make a few natural swirls across the surface. The raised portions will turn lightly golden as the casserole bakes.

Cut the remaining butter into small pieces and scatter it across the top.

If you are baking the casserole immediately, place it in a preheated 350°F oven. Bake uncovered for 25 to 30 minutes or until it is hot throughout.

For a slightly browner surface, place the casserole under the broiler for a minute or two. Watch it carefully because the top can brown quickly.

Make-Ahead Mashed Potato Casserole Instructions

To prepare the casserole ahead of time, follow the recipe through the point of spreading the potatoes in the baking dish.

Let the potatoes cool for approximately 20 minutes. Cover the dish tightly with foil or a fitted lid and refrigerate it for up to two days.

Do not leave the casserole at room temperature until it is completely cold. Once the heavy steam has stopped rising, cover and refrigerate it.

On Thanksgiving Day, remove the casserole from the refrigerator approximately 30 minutes before baking. This takes some of the chill off the baking dish and helps the center heat more evenly.

Place the covered casserole in a 350°F oven and bake for 30 minutes. Carefully remove the foil and continue baking for another 15 to 20 minutes.

The casserole is ready when the edges are bubbling slightly and the center is hot.

If the potatoes appear dry around the edges, drizzle a tablespoon or two of warm milk over the surface before adding the butter and baking.

Making Room In The Oven

The casserole can bake at the same temperature as many other Thanksgiving side dishes. A difference of 25°F in oven temperature is generally manageable, although the baking time may need to shorten or lengthen.

If the turkey is resting after it comes out of the oven, use that time to bake the potatoes. A large turkey should rest before carving, which gives the casserole time to heat.

Once the mashed potato casserole is hot, cover it loosely with foil. It will remain warm for approximately 20 to 30 minutes.

Optional Toppings

I prefer to keep the topping simple with butter because it pairs well with turkey and gravy. However, you can add a topping if you would like to change the recipe.

Sprinkle shredded cheddar cheese over the potatoes during the final 10 minutes of baking. You can also add chopped chives, sliced green onions or cooked crumbled bacon after the casserole comes out of the oven.

For a lightly crisp topping, combine melted butter with seasoned breadcrumbs and sprinkle it over the casserole before baking.

Keep in mind that a heavy topping can compete with the gravy. For a traditional Thanksgiving meal, stick with butter and a small amount of fresh parsley or chives.

Storing And Reheating Leftovers

Cover leftover mashed potato casserole and refrigerate it within two hours. It will keep in the refrigerator for up to four days.

Reheat individual portions in the microwave with a small pat of butter or a splash of milk. Cover the potatoes loosely so they do not dry out.

To reheat a larger amount, place it in a covered baking dish and bake at 325°F until hot. Stir in a little warm milk if the potatoes have become too thick.

Leftover mashed potatoes can also make great potato cakes, shepherd’s pie or as a topping for leftover turkey pot pie.

Enjoy! Mary

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