Mashed Potato Casserole

This outrageously delicious Mashed Potato Casserole is the best way to prepare mashed potatoes fresh or ahead of time! Fully loaded with butter, bacon, green onions, sour cream, and plenty of cheese, serve this flavorful, no-fuss side dish on busy weeknights and throughout the holiday season.

Loaded Mashed Potato Casserole Recipe

Oh, the holidays! So much fun, no? Truthfully, my opinion of the holiday season changes rapidly, as does my enthusiasm toward hosting and cooking (ah, the inconsistency that is life).

Burnout, exhaustion, who knows? But planning and hosting for so many other people at such an important time of the year is a heck no for me. Instead, I take the easy way out. Surprising? Maybe. But in exchange, I always offer something delicious.

This loaded mashed potato casserole is one of my favorite holiday offerings. It’s a win-win for all! Here’s the thing—you can make this super easy casserole ahead of time, up to two days before you plan on serving it. And it travels well. With this thick and creamy potato casserole, there’s no need to stress about anything spilling or sloshing as you try to drive down the road. We’ve all been there. Let’s not go back.

The best part, though, is that this mashed potato casserole tastes really good—arguably the most important part, yes? After all, you are providing the potatoes of the party. Mashed with cream, butter, and sour cream and generously seasoned with salt and black pepper, these potatoes are then loaded with salty bacon, green onions, and cheese—heaven.

Key Ingredients and Substitutions

Find the printable recipe with measurements in the recipe card below.

• Potatoes: I prefer using Russet potatoes for mashed potatoes because they’re starchy and fluffy. However, if Russets aren’t available, Yukon Gold and red potatoes will also work. Learn more about the different types of potatoes here.
• Butter: Adds richness and a smooth, creamy texture. It also enhances the overall flavor of the potatoes, especially if you use salted butter.
• Heavy Cream: To make the mashed potatoes rich and creamy.
• Milk: More or less milk is added depending on how thick you like your mashed potatoes.
• Sour Cream: For tang and extra creaminess.
• Salt & Black Pepper: To season the mashed potatoes. Optional seasonings to consider include onion powder and garlic powder.
• Bacon: Cooked bacon adds an irresistible salty, smoky, and savory depth of flavor. Add as much or as little as you’d like!
• Green Onion: Freshly chopped onions (or chives) have a mild onion flavor that cuts through the richness of the potatoes.
• Cheese: Cheese is mixed both into the mashed potatoes and sprinkled over the top. In this recipe, I’ve included freshly shredded mozzarella and cheddar cheese, but any type of melty cheese will work.

Cooking Tips

• If you plan to make this casserole ahead, add an additional 1 cup of milk. The mashed potatoes will firm up and thicken overnight, and with the addition of extra milk, they will have the same consistency once reheated as when they were first made.
• Drain the potatoes thoroughly to avoid watery mashed potatoes. I like to let them sit in the colander for a few minutes to release steam.
• Add the butter before the milk and cream for a smoother, creamier texture.
• Don’t overmix the potatoes. I even have a hard time with this one, but it’s so important to stir and mash your potatoes gently. If possible, use a potato masher, a ricer, or a food mill. Overworking may result in gluey potatoes.
• This recipe is just a guideline—season the potatoes according to your own preference. For example, I add way more than one teaspoon of salt. I may also add a teaspoon of garlic powder or onion powder. Sometimes, I may even add some cream cheese (usually about four ounces) if I want my casserole to be extra rich.

How to Make Mashed Potato Casserole

1. Prepare the potatoes: Peel and cut the potatoes into even-sized pieces (peeling is optional if using Yukon Gold or red potatoes). Preheat the oven to 375 degrees Fahrenheit and lightly grease a 4-inch deep 9×9-inch casserole dish (or similar).

2. Boil the potatoes: Place the potatoes in a large pot and cover with cold, salted water. Bring the pot to a boil over high heat, then reduce the heat to medium to maintain a rapid simmer. Cook until the potatoes are fork-tender (about 8-12 minutes).

3. Mash: Drain the potatoes in a large colander. Let them rest for a few minutes to release steam before returning them to the empty pot. Add the butter and gently mash using your favorite potato masher before adding the heavy cream and 1/2 cup of milk. Mash again until the cream and milk are fully combined and the potatoes are fluffy.

• NOTE: If you are making this mashed potato casserole ahead, add an additional 1 cup of milk. It’s ok if the potatoes are a little loose or wet.

4. Load the potatoes: Mix in the sour cream, salt, and pepper then fold in the bacon, green onions, mozzarella, and half of the cheddar cheese.

5. Assemble the casserole: Pour the potatoes into the prepared casserole dish and sprinkle the remaining cheddar cheese over the top.

• NOTE: If you are making this dish ahead of time, cover it tightly with foil and refrigerate it for up to 2 days. Remove it from the refrigerator 1-2 hours before baking, so it has time to reach room temperature throughout and cook more evenly in the oven.

6. Bake: Bake for 25 minutes or until the cheese is melted and the potatoes are lightly browned on top. Remove from the oven and garnish with freshly sliced chives, green onions, or more bacon, if desired.

Storage and Leftovers

Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Though the leftovers are delicious, they are never quite as creamy and luscious as when first made. You may want to reheat smaller portions on the stovetop with a bit of cream or milk.

I have not tried freezing this recipe, so I cannot speak for the results after thawing and reheating.

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