My favorite part of this Mashed Potato Casserole is when you scoop through that golden crust and hit the creamy layer underneath. The onions give crunch, Cheddar adds richness, and the sour cream keeps the potatoes smooth. It’s impossible to stop at one serving.

A Mashed Potato Casserole topped with crispy fried onions and sliced green onions, served in an oval dish on a table. — Mashed Potato Casserole. Photo Credit: Hungry Cooks Kitchen.

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I make this side dish for Thanksgiving dinner, Christmas gatherings, and Sunday suppers when I need something that feeds a crowd without much fuss. It’s rich, cheesy, and creamy, and has become my go-to potluck dish. It’ll keep in the fridge for about 3 to 4 days or in the freezer for up to 3 months, which makes it perfect for meal prep.

Ingredients You’ll Need

You’ll need all the ingredients shown in the photograph below.

A top view of ingredients for a Mashed Potato Casserole-style twice-baked potatoes, including russet potatoes, cheddar cheese, sour cream, butter, milk, breadcrumbs, fried onions, green onions, and seasonings. — Mashed Potato Casserole Ingredients. Photo Credit: Hungry Cooks Kitchen.

How to Make Mashed Potato Casserole with Step-By-Step Instructions

Scroll down for the full recipe card containing a full printable recipe and measurements in both US customary and metric units.

Let me walk you through making this crowd-pleasing side dish that comes together more easily than you’d think.

Prepare Your Baking Dish and Oven

Set your oven to 375°F and grab a 9 × 13-inch baking dish. Butter it generously so nothing sticks.

I love using my ceramic casserole dish because it heats evenly and looks nice on the dining table.

Boil the Potatoes Until Tender

Peel, rinse, and slice your potatoes into chunks. Soak them in a large pot of generously salted water, so the salt seasons the potatoes from the inside out, which makes a huge difference in the final flavor.

Now, boil over high heat and cook for 20 to 25 minutes, until the potatoes are completely fork-tender.

Drain them really well; this is where many people end up with watery casseroles, so take an extra minute to let all that moisture steam off. I’m using a deep stainless steel colander with many tiny holes for fast draining.

Mash the Potatoes Smooth

Once they’re fully drained, mash them until they’re completely smooth and lump-free using a potato masher or an electric mixer to make this step effortless and get that perfect creamy texture without any arm workout.

You can also mash them through a potato ricer right over the empty pot if you haven’t returned them yet after draining, and honestly, it’s quite satisfying watching them come out of the holes as fluffy shreds.

Mix in the Creamy Ingredients

Stir your butter, milk, sour cream, garlic powder, onion powder, and half of the shredded Cheddar cheese into your mashed potatoes, and season with salt and black pepper.

I love shredding my own cheese because it melts more smoothly than pre-shredded cheese, and that’s why I always keep a box grater handy for things like this.

Mix everything until well blended, and you achieve the creamy consistency you like. The sour cream is the secret here; it adds this incredible tang and keeps everything moist during baking.

Assemble the Casserole

Spread your mashed potato mixture evenly into the prepared baking dish and sprinkle the remaining Cheddar cheese over the top.

Add the breadcrumbs for that textured golden crust that contrasts beautifully with the creamy potatoes underneath.

An oval baking dish filled with Mashed Potato Casserole, topped with shredded cheese and breadcrumbs, sits beside a bowl of crispy fried onions. — Top with cheese and breadcrumbs, bake for 25–30 minutes until golden and bubbly, then garnish with fried and green onions before serving warm.

Bake Until Golden

Place your dish in the oven and bake for 25 to 30 minutes. You’re looking for the top to turn golden brown and the cheese to melt completely. The edges should be bubbling just slightly.

If you want to take your presentation up a notch, finish it under the broiler for 2 minutes, just watch it closely because the cheese and breadcrumbs can go from perfectly golden to burnt in seconds under that intense heat.

Garnish and Serve

Let the casserole rest for 5 minutes after you pull it from the oven. This lets everything firm up so it holds together when you scoop it.

Garnish with crispy fried onions and chopped green onions right before serving. The contrast between the creamy base and crunchy toppings is what makes this casserole truly addictive. Finally, serve warm and enjoy!

If you’re taking the casserole to a potluck, cover it tightly with foil and wrap the dish in a kitchen towel to help keep it protected during transport. Pop the dish into an insulated casserole carrier to keep it warm until serving time.

Mashed Potato Casserole

I love making this Mashed Potato Casserole because it's creamy, cheesy, and has the most incredible golden crust on top. The sour cream keeps the potatoes smooth and adds a subtle tang, while the Cheddar melts into every bite for rich, savory flavor. The crispy fried onions and breadcrumb topping create the perfect balance to the creamy base underneath. I make this for Thanksgiving, Christmas, holiday potlucks, and cozy family dinners because it's easy to prep ahead and always disappears fast. It will stay fresh in the fridge for 3 to 4 days or freeze well for up to 3 months.

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Prep Time: 20

Cook Time: 55

Total Time: 1 15

Course: casserole, Dinner, Side Dish

Cuisine: American

Keyword: Mashed Potato Casserole

Servings:

Calories: 422kcal

Author: Mandy Applegate

Equipment

Stainless steel colander

Ingredients

4 pounds russet potatoes peeled and cut into chunks
2 cups Cheddar cheese shredded
1 cup milk
1 cup sour cream
½ cup unsalted butter
1 teaspoon garlic powder
1 teaspoon onion powder
Salt and black pepper to taste

Toppings:

¼ cup chopped green onions
2 tablespoons breadcrumbs
1 cup crispy fried onions

US Customary – Metric

Instructions

Set the oven to 375°F (190°C) and butter a 9 × 13-inch baking dish.
Place the potato chunks in a large pot of generously salted water. Bring to a boil and cook for 20 to 25 minutes, or until the potatoes are fork-tender. Drain well.
4 pounds russet potatoes
Transfer the drained potatoes to a large mixing bowl. Mash until smooth and lump-free using a potato masher or an electric mixer.
Stir in the butter, milk, sour cream, garlic powder, onion powder, half of the shredded Cheddar cheese, and salt and black pepper. Mix until creamy and well blended.
2 cups Cheddar cheese, 1 cup milk, 1 cup sour cream, ½ cup unsalted butter, 1 teaspoon garlic powder, 1 teaspoon onion powder, Salt and black pepper
Spread the mashed potato mixture evenly into the prepared baking dish. Sprinkle the remaining Cheddar cheese and breadcrumbs evenly over the top.
2 tablespoons breadcrumbs
Place the dish in the oven and bake for 25 to 30 minutes, or until the top is golden brown and the cheese is melted.
Let the casserole rest for 5 minutes. Garnish with crispy fried onions and chopped green onions before serving.
¼ cup chopped green onions, 1 cup crispy fried onions

Video

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Notes

Here are my tried-and-true tips for making this mashed potato casserole turn out perfect every time:

Drain the potatoes thoroughly: After boiling, let them sit in the colander for a full minute to steam off excess moisture. Watery potatoes mean a watery casserole that won’t hold its shape.

Don’t overmix the potatoes: Once you add the dairy ingredients, mix just until combined. Overworking the potatoes activates too much starch and makes them gummy instead of fluffy. You can use Yukon Golds for extra creaminess.

Use room temperature dairy: Let your butter, milk, and sour cream sit out for 30 minutes before mixing. Cold dairy can make the potatoes seize up and turn gluey. You can also swap half the milk for heavy cream for a silkier texture.

Adjust cheese to your taste: If you want it extra cheesy, add another half cup of Cheddar to the potato mixture. For a milder version, use sharp white Cheddar instead of the orange variety, or fontina for a more buttery flavor.

Add crispy bacon for extra richness: Crumble 6 to 8 strips of cooked bacon into the mashed potato mixture before baking, or sprinkle it on top with the fried onions for a smoky, savory crunch that takes this casserole over the top.

Store properly: Store leftovers in an airtight container in the fridge for 3 to 4 days or freeze portions for up to 3 months. Reheat in the oven or microwave until warmed through, adding a splash of milk if needed.

Nutrition

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How to Store Leftovers

Cover the fully cooled casserole dish tightly with foil or transfer portions to stackable airtight containers. It stays fresh in the refrigerator for 3 to 4 days and reheats beautifully in the oven or microwave.

For longer storage, you can freeze this casserole for up to 3 months. I usually portion it out into freezer-safe containers before freezing so I can pull out just what I need.

When you’re ready to serve, thaw it overnight in the fridge, then reheat until warmed through. The texture stays remarkably creamy even after freezing, though you might want to add a splash of milk when reheating if it seems dry.

What to Serve With Mashed Potato Casserole

This casserole pairs perfectly with roasted meats like turkey, ham, or prime rib, which makes it ideal for holiday meals. I also love serving it alongside grilled chicken or pork chops for Sunday dinners.

For vegetables, I like to balance the richness with something bright like roasted Brussels sprouts, green beans almondine, or a crisp garden salad. You could also serve it with cranberry sauce or applesauce for a sweet contrast.

More Easy Recipes for You to Try at Home

I bet you’ll love these other casseroles I’ve made, with the same creaminess and comforting layer of cheese as this one:

About the Author

A woman with long brown hair is smiling and standing with her arms crossed. She is wearing a sleeveless, black and white diamond-patterned dress.

Hey there! I’m Mandy

Mandy Applegate is a home cook, food blogger, and writer who believes the best meals are the ones shared with the people you love.

She’s all about easy recipes that taste amazing, the kind that make ordinary days feel a little more special and remind you why cooking at home matters.

She has been published on NBC, the Daily News, the Boston Herald, and the Chicago Sun-Times, amongst many others.

Mashed Potato Casserole

Ingredients You’ll Need