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Cheesy Mashed Potato Casserole

Cheesy Mashed Potato Casserole—if there’s one dish that transcends comfort food, this is it. Its ingredients are humble, its preparation simple, and yet it manages to seduce the senses. 

A casserole dish topped with chicken and parsley.

This Cheesy Potato Casserole is both completely unpretentious and profoundly satisfying, a humble masterpiece that beckons us to discover its secrets of cheesy, creamy, mashed potato bliss, with a raucous topping of buttery, crisp Ritz crackers and sultry caramelized onions.

If there’s one thing I can’t resist, it’s a warm and cheesy potato casserole. It’s perfect alongside roast meats and has the perfect countenance to stand up to a Thanksgiving turkey or a Christmas Ham. 

Why You’ll Love This Dish

This crave-worthy mashed potato casserole is one of those perfect comfort food dishes that combines humble ingredients in a way that is outrageously mouthwatering. Just look at that crispy, buttery cracker crumb topping and that layer of cheesy potato goodness!

  • So cheesy: Who can resist the allure of melted cheddar cheese? This casserole is loaded with it, creating layers of gooey, cheesy deliciousness.
  • Caramelized onions: Slow-cooked, caramelized onions take on a delightfully unctuous sweetness and add depth and complexity to the dish. They’re the secret ingredient that elevates the flavor.
  • Crunchy topping: Thanks to the crushed Ritz crackers—so flaky and buttery!—you get a delightful crunch with every bite, adding textural contrast to the smooth mashed potatoes below.
  • Quick and easy: With a total prep-and-cook time of just 20 minutes, this dish is perfect for a weeknight dinner, a last-minute potluck addition, or a low-effort, high-reward side for a holiday feast.
Cheesy mashed potato crackers.

Ingredients You Need

You only need a handful of humble ingredients to create this downright sexy potato casserole dish. Here’s what you’ll need:

  • Salted butter: This adds a rich and buttery flavor to the dish.
  • Onion: You can use white or yellow onion. Slice it thinly and it will caramelize beautifully and provide an intriguing hint of sweetness.
  • Garlic: Minced fresh garlic adds bold aromatic flavor.
  • Ritz Crackers: Yes, that beloved childhood treat is the coveted guest star of this potato show. They’re the secret to the irresistible crunchy topping. If you don’t have any Ritz crackers, you could substitute panko bread crumbs.
  • Mashed potatoes: Prepare 4 cups of mashed potatoes. For best results, use Yukon or Russet potatoes for this dish.
  • Parmesan cheese: Mixed into the potatoes, this adds extra cheesiness and a satisfying layer of umami.
  • Seasonings: The flavors in this dish are basic but rich and on point. The only seasonings you need to add are salt and pepper.
  • Cheddar cheese: Shredded cheddar cheese is what makes it so cheesy good!
  • Fresh parsley: The finishing touch that makes it look especially divine. You could substitute fresh chive, if you like.

Remember, you can always experiment and customize your ingredients to suit your taste. For instance, you can use different types of cheese for a unique flavor twist, add crispy bacon for an extra layer of flavor and crunch, or add a dollop of sour cream or cream cheese for added creamy richness. Make it a truly loaded mashed potato casserole!

How to Make It

Here’s a simplified step-by-step guide to creating this irresistible mashed potato casserole recipe:

  1. Get ready: Set your oven to 400°F and lightly grease a 9-by-13-inch baking dish.
  2. Caramelize the onions: Cook the onions and garlic in butter in a skillet over medium heat, stirring occasionally, for about 10 minutes total, until the onions are browned and soft and their natural sweetness has emerged.
  3. Make the topping: Mix the cracker crumbs with the caramelized onions.
  4. Prepare the casserole: In the greased baking dish, combine the mashed potatoes with the grated parmesan cheese, salt, and pepper using a wooden spoon or a potato masher. Spread the potato mixture evenly in the pan and sprinkle the shredded cheese over the top.
  5. Bake and brown: When you’re ready to bake the dish, cover and bake it until the cheese is melted and nicely browned, which usually takes about 15 minutes.
  6. Add the topping: Remove the casserole from the oven and generously top it with the cracker and caramelized onion mixture.
  7. Garnish and serve: Finish it off by garnishing with minced fresh parsley, and serve it piping hot.

This dish is a crowd-pleaser that you can whip up with ease. It’s the perfect comfort food that can elevate any meal. and it’s easy to make ahead of time, too. 

A plate of potato casserole with onions on it.

Make it ahead to Simplify your holiday meal prep

This is a perfect side to make ahead for an elaborate holiday meal. You can cook the potatoes, mash the potatoes, caramelize the onions, and put the casserole together several days before you’ll serve them. Just cover tightly and refrigerate for up to 5 days.

You can reheat your make-ahead mashed potato casserole by covering it with foil and heating in a 400°F oven for 10 minutes or so, then taking off the covering and cooking another few minutes to crisp up the topping.

A casserole dish filled with mashed potatoes and cheese.

What to Serve with It

This Cheesy Mashed Potato Casserole is a versatile dish that pairs well with various main courses. The savory, homey flavors complement roasted chicken, turkey, or beef perfectly.

A juicy Grilled Flank Steak with Chile Butter is a heavenly match. Even a more delicate protein like Air Fryer Salmon is complemented by the potato-y goodness.

This casserole is the ultimate comfort food, and its adaptability makes it a go-to side dish for various occasions. Serve it with Instant Pot Ham for Christmas or Easter, with Air Fryer Turkey Legs for Thanksgiving, or with Air Fryer Lamb Chops for an elegant Sunday dinner.

Other holiday-friendly sides will fit right into any of these meals. I’ve made this for Thanksgiving along with my famous Instant Pot Duck Confit and Green Bean Salad and it’s been a huge hit! Other great pairings include Air Fryer Brussels Sprouts or Air Fryer Artichokes, or Dry Fried Green Beans to round out a meal.

A casserole dish with a spoon in it.

Cheesy Potato Casserole with Ritz Crackers and Caramelized Onion

Robin Donovan
Everyone loves mashed potatoes, and this mashed potato casserole takes them over the top. m in the creamy delight of Cheesy Potato Casserole with Ritz Crackers and Caramelized Onion. This easy-to-make, comforting dish boasts layers of flavor, from the rich, gooey cheese to the satisfying crunch of buttery Ritz crackers. A true crowd-pleaser!
5 from 9 votes
Prep Time 5 minutes
Cook Time 15 minutes
Total Time 20 minutes
Course Side Dish, Side Dish Recipes
Cuisine American
Servings 6 servings
Calories 378 kcal


  • 4 tablespoons salted butter divided
  • 1 medium onion thinly sliced
  • 1 garlic clove peeled and minced
  • 1 cup ritz crackers roughly crushed (
  • 4 cups mashed potato 1 ¾ pounds
  • ½ cup grated parmesan cheese
  • ¼ teaspoon kosher salt
  • ¼ teaspoon freshly ground black pepper
  • 1 cup 8 ounces shredded sharp cheddar cheese
  • 3 tablespoons minced fresh parsley


  • Preheat the oven to 400°F and lightly grease a 9-by-13-inch baking dish.
  • Heat a skillet over medium heat and add 2 tablespoons of the butter and the sliced onion. When butter is melted, stir and reduce the heat to low. Cook for 2 minutes then add the garlic cloves and cook, stirring occasionally, for 8 minutes. Remove the skillet from the heat and stir in the cracker crumbs.
  • While onions are cooking, melt the remaining 2 tablespoons of butter.
  • In the baking dish, combine the mashed potato and the parmesan cheese in the baking dish. Season with salt and pepper. Spread the potato mixture into an even layer in the baking dish and sprinkle the cheddar on top.
  • Bake in the oven until the cheese melts and is nicely browned, about 15 minutes.
  • Remove the casserole from the oven and top with the cracker and caramelized onion topping.
  • Garnish with the parsley and serve hot.


If you’re wondering what type of potatoes to use for mashing and turning into this decadent casserole, the best choices are Yukon gold potatoes or Russet potatoes because they make the best mashed potatoes.
You can make this casserole several days ahead. Store it covered in the refrigerator for up to 5 days. You can even freeze itfor up to 1 month, but be warned that potatoes can become grainy when they’re frozen.


Calories: 378kcalCarbohydrates: 42gProtein: 11gFat: 19gSaturated Fat: 10gPolyunsaturated Fat: 2gMonounsaturated Fat: 5gTrans Fat: 0.4gCholesterol: 46mgSodium: 557mgPotassium: 512mgFiber: 3gSugar: 3gVitamin A: 499IUVitamin C: 34mgCalcium: 240mgIron: 1mg
Keyword casserole, christmas side, easter side, mashed potatoes, side dish, thanksgiving side
Tried this recipe?Let us know how it was!
Cheesy mashed potato casserole pinterest pin.
By on October 17th, 2023
Photo of Robin Donovan

About Robin Donovan

Robin Donovan is the creative force behind All Ways Delicious. She's a writer, recipe developer, photographer, and cookbook author with more than 40 books to her name, including the bestselling Ramen for Beginners, Ramen Obsession, and Campfire Cuisine. Her work has been featured in major publications, both print and digital, including MSN, Cooking Light, Fitness, Buzzfeed, and Eating Well. More about Robin

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7 thoughts on “Cheesy Mashed Potato Casserole”

  1. I couldn’t resist trying out this Cheesy Mashed Potato Casserole, and it turned out to be a flavor bomb! Definitely a new family favorite! Thank you.

  2. 5 stars
    Creamy, fluffy, and had a wonderful crispy topping that I so love. It paired perfectly with some grilled chicken and chips. I’m thinking of adding more garlic and fresh herbs next time for an extra flavor kick!

  3. 5 stars
    I had some leftover mashed potatoes and I wasn’t sure what to do with them, this was the perfect recipe! It was so cheesy and delicious! My family ate it up with no more leftovers!

  4. 5 stars
    I tried this recipe out last weekend to test it for an upcoming Friendsgiving and could not be happier with the result! It’s got everything you love about a good casserole going on and it’s super easy to make. I’m sure it will be a hit!

  5. 5 stars
    I have never put Ritz crackers in my mashed potatoes… until now! It was the perfect buttery, salty addition to the cheesy potatoes. I cannot wait to make this again for my family at Thanksgiving.

  6. 5 stars
    I added some crispy bacon bits to the top, and it was divine! The whole family raved about it. This casserole will be a regular on our menu.


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