Mashed Potato Casserole is the ultimate comfort food side dish—creamy, cheesy, and golden-topped with just the right amount of texture and flavor. Whether you’re hosting a holiday meal, planning a potluck, or looking to elevate your weeknight dinner, this baked version of classic mashed potatoes adds richness and depth to a traditional favorite.
What makes this casserole stand out is the addition of sour cream, cheddar cheese, and Parmesan, giving it a tangy, savory profile with a luscious texture. It’s whipped to creamy perfection, folded with melty cheese, and then baked until lightly golden for a soft-on-the-inside, slightly crispy-on-the-top experience. Optional toppings like breadcrumbs, chives, or even a little bacon can make this dish as decadent or as simple as you’d like.
Best of all, it’s make-ahead friendly and reheats beautifully, making it a go-to for holiday prep or feeding a crowd. With ingredients you likely already have on hand, Mashed Potato Casserole is a reliable, crowd-pleasing side dish you’ll find yourself making again and again.
Preparing the Potatoes for Creaminess and Flavor
The key to a perfect Mashed Potato Casserole starts with selecting the right type of potatoes and cooking them properly to achieve a smooth, fluffy base full of flavor.
Begin by choosing either russet potatoes or Yukon golds.
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Russet potatoes are high in starch and create a classic, fluffy mash.
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Yukon golds are slightly waxy with a natural buttery flavor and yield a creamier texture.
Peel and chop 3 pounds of potatoes into evenly sized chunks to ensure they cook at the same rate. Place the chopped potatoes into a large pot and cover them with cold, salted water. Starting with cold water helps the potatoes cook evenly from the inside out.
Bring to a boil over medium-high heat and cook for 15–20 minutes, or until the potatoes are fork-tender. Avoid overcooking to prevent them from becoming waterlogged, which can lead to a gummy mash.
Once done, drain the potatoes thoroughly and return them to the pot. This step helps evaporate any remaining moisture and keeps the mash light and fluffy. Warm potatoes also absorb ingredients better, making this the perfect time to start building flavor.
Mashed Potato Casserole Make Ahead and Loaded
Ingredients
Method
- Preheat oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
- Place the potatoes in a large pot, cover with cold water, and add a generous pinch of salt. Bring to a boil and cook until fork-tender, about 15–20 minutes.
- Drain the potatoes well and return them to the pot.
- Add butter, sour cream, milk, garlic powder, onion powder, salt, and pepper. Mash until smooth and creamy.
- Stir in the shredded cheddar cheese and green onions (if using).
- Transfer the mashed potatoes to the prepared baking dish and spread evenly.
- Sprinkle the top with Parmesan cheese and any optional toppings like breadcrumbs or extra shredded cheese.
- Bake uncovered for 25–30 minutes, or until heated through and lightly golden on top.
- Let cool slightly before serving. Garnish with chopped chives or parsley if desired.
Notes
- Use starchy potatoes like russets or Yukon golds for the creamiest texture
- Start with cold water when boiling to ensure even cooking
- Drain thoroughly and mash while hot for best results
- Add cheese and green onions for flavor and texture
- Top with Parmesan, breadcrumbs, or more cheese for a golden crust
- Chill assembled casserole up to a day in advance before baking
- Reheat gently to preserve texture, either in the oven or microwave
- Freeze leftovers or unbaked casserole for future meals
- Customize mix-ins like bacon, garlic, or herbs to suit your taste