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Air Fryer Mashed Potato Casserole

Air Fryer Mashed Potato Casserole is my go-to when I need a comfort side dish that delivers big without tying up the oven. Creamy, buttery mashed potatoes packed with cheddar, sour cream, and garlic powder, topped with crispy fried onions and breadcrumbs and baked until perfectly golden and crispy on top. The air fryer makes the topping crispier than any oven version I've ever made. I make it for Thanksgiving, Christmas, Easter, and family dinners because it feeds a crowd and is completely make-ahead friendly. Leftovers keep in the fridge for 3 to 4 days or freeze for up to 3 months.
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Prep Time: 20 minutes
Cook Time: 45 minutes
Total Time: 1 hour 5 minutes
Course: casserole, Side Dish
Cuisine: American
Keyword: Air Fryer Mashed Potato Casserole
Servings: 10
Calories: 422kcal

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

  • 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 into an air fryer-safe baking dish that fits your basket or tray. Top with the remaining Cheddar cheese and breadcrumbs.
    2 tablespoons breadcrumbs
  • Place the dish in the air fryer basket and cook at 350°F (180°C) for 15 to 20 minutes, or until the top is golden and the cheese is melted.
  • Let rest for 5 minutes, then garnish with crispy fried onions and chopped green onions before serving.
    ¼ cup chopped green onions, 1 cup crispy fried onions

Notes

Here are a few tips I've picked up from making this casserole that make a real difference in the final result.
Use room-temp butter and milk: Cold butter and milk don't blend as smoothly into hot potatoes. Let them sit out for 20 to 30 minutes before mixing in for the creamiest result.
Mash well before mixing: Get the potatoes completely smooth before adding the other ingredients. Mixing in chunks makes it harder to break down evenly once the dairy is in.
Check your dish size: Use an air fryer-safe baking dish that fits your specific basket or tray with a little clearance on the sides. If it's too tight, the hot air can't circulate, and the top won't crisp up properly.
Watch the top closely: Every air fryer runs slightly differently. Start checking at 15 minutes so the breadcrumb and cheese topping go golden without burning.
Add toppings last: Always wait until just before serving to add the crispy fried onions and green onions. Adding them before air frying will make the onions soggy and the green onions wilted.
Store properly: Cover the cooled dish or transfer portions to airtight containers to chill in the fridge for 3 to 4 days or freeze for up to 3 months. Thaw frozen portions in the refrigerator overnight before reheating in the microwave, oven, or air fryer.

Nutrition

Calories: 422kcal | Carbohydrates: 40g | Protein: 11g | Fat: 25g | Saturated Fat: 14g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 5g | Trans Fat: 0.4g | Cholesterol: 64mg | Sodium: 237mg | Potassium: 858mg | Fiber: 3g | Sugar: 3g | Vitamin A: 720IU | Vitamin C: 11mg | Calcium: 246mg | Iron: 2mg
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