Cheesy Mashed Potato Casserole With Sour Cream

potato casserole with sour cream and cheddar cheese
Diana Rattray
Prep: 15 mins
Cook: 25 mins
Total: 40 mins
Servings: 6 to 8 servings
Nutrition Facts (per serving)
363 Calories
21g Fat
38g Carbs
8g Protein
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Nutrition Facts
Servings: 6 to 8
Amount per serving
Calories 363
% Daily Value*
Total Fat 21g 27%
Saturated Fat 12g 61%
Cholesterol 58mg 19%
Sodium 525mg 23%
Total Carbohydrate 38g 14%
Dietary Fiber 4g 13%
Total Sugars 3g
Protein 8g
Vitamin C 17mg 83%
Calcium 161mg 12%
Iron 2mg 10%
Potassium 963mg 20%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)

This mashed potato casserole has it all. You can it make ahead, it's easy to put together, it keeps well as leftovers, and it's simply delicious. Creamy potatoes coated with cheese and sour cream make a succulent combination that's just perfect to serve with any main protein you are planning on. The oven does most of the work and then your hands are free to prep the rest of the meal so you can serve everything while the casserole is still hot and bubbly. Pork tenderloin, roasted beef, chicken breast, and even fish make a wonderful meal alongside this simple and tasty recipe.

A few pantry staple ingredients and 40 minutes are all that you need to serve this dish. We used Cheddar cheese as it melts well and has a wonderfully tangy and rich flavor, but any cheese that melts well, like full-fat mozzarella or Colby Jack, makes a wonderful addition. The sour cream adds a bright note to the casserole and the green onions bring a welcome herby touch into the mix.

We recommend using moderate to high-starch potatoes like russets, Idaho baking potatoes, or Yukon Gold. Remember to always grate the cheese from a block; already shredded cheese is filled with anti-caking agents that make it less likely to melt as this recipe needs. Besides, it's better for your budget to buy the cheese by the pound than to buy it shredded.

Ingredients

For the Potatoes:

  • 2 1/2 to 3 pounds potatoes, washed

  • 2 teaspoons kosher salt

For the Casserole:

  • 8 tablespoons melted butter, divided

  • 3/4 cup sour cream

  • 1/4 cup milk , or half-and-half; or as needed

  • 6 to 8 green onions, chopped

  • 1 cup shredded Cheddar cheese

  • Salt and pepper to taste

Steps to Make It

Cook the Potatoes

  1. Gather the ingredients.

  2. Heat the oven to 400 F. Lightly butter a 2-quart baking dish or spray it with nonstick cooking spray. 

  3. Peel the potatoes and cut them into even-sized chunks.

  4. Place the potatoes in a large saucepan or stockpot; cover them with water and add 2 teaspoons of kosher salt. Place the pan over high heat and bring the potatoes to a boil.

  5. Cover the pot, reduce the heat to medium-low, and boil the potatoes for about 20 minutes, or until they are very tender.

  6. Drain thoroughly.

Mash the Potatoes and Assemble

  1. Mash the potatoes with 6 tablespoons of the butter, sour cream, milk, green onions, and about 3/4 cup of the cheddar cheese.

  2. If needed, thin with more milk or cream. Add salt and pepper to taste.

  3. Spoon the potato mixture into the prepared baking dish. Drizzle the remaining 2 tablespoons of melted butter over the potatoes.

  4. Bake in the preheated oven for 25 minutes, or until the casserole is lightly browned. Scatter the remaining shredded cheddar cheese over the casserole and return it to the oven for a few more minutes, or just until the cheese has melted.

  5. Enjoy!

    Mashed potato casserole.
     Diana Rattray

Can I Make the Casserole Ahead of Time?

Yes. Simply assemble as directed, but reserve the cheese and butter needed to make the topping. Let it cool off slightly before covering it with tin foil and placing it in the refrigerator. Keep for up to 2 days before using. Right before baking, drizzle 2 tablespoons of butter and the remaining cheese and allow 5 to 10 extra minutes in the oven for it to heat up thoroughly.

Other Delicious Add-Ons

There are many ways in which you can vary this tasty recipe:

  • Meaty: Add 1 cup of finely chopped ham or 1/2 cup of crumbled cooked bacon.
  • Herby: Replace the green onions with a few tablespoons of fresh chopped chives or add a tablespoon or two of fresh chopped parsley right before serving.
  • Buttered breadcrumbs topping: Instead of drizzling the 2 tablespoons of butter over the potatoes, mix them with about 1/2 to 1 cup of soft breadcrumbs. Sprinkle the buttered breadcrumbs over the potatoes and bake as directed, or until the crumbs are golden brown.
  • Extra cheese: Mix the mashed potatoes with 1 cup of Cheddar cheese. Follow the method as directed but add 2/3 cup of grated Parmesan cheese after 25 minutes in the oven and allow the cheese topping to melt and get crispy.