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Make Ahead Mashed Potato Casserole

The creamiest make-ahead Thanksgiving side: silky mashed potatoes whipped with cream cheese, sour cream, and butter, topped with a golden melted cheddar crust. Assemble up to 3 days ahead, then just bake.
Print Recipe
Prep Time 20 minutes
Cook Time 1 hour
Total Time 1 hour 20 minutes
Course Side Dish
Cuisine American
Servings 12 servings
Calories 342 kcal

Ingredients
  

  • 5 pounds Yukon Gold potatoes peeled and cut into 1 1/2-inch chunks
  • 1 tablespoon kosher salt plus more to taste
  • 8 ounces cream cheese softened
  • 1/2 cup unsalted butter (1 stick) softened, plus more for the dish
  • 1 cup sour cream at room temperature
  • 3/4 cup whole milk warmed
  • 1 1/2 teaspoons garlic powder
  • 1/2 teaspoon freshly ground black pepper
  • 2 cups shredded sharp cheddar cheese divided
  • 1/4 cup chopped fresh chives or green onions for serving

Instructions
 

  • Place the potato chunks in a large pot and cover with cold water by 2 inches. Stir in 1 tablespoon of kosher salt, cover, and bring to a boil over high heat.
  • Reduce the heat to medium-low and simmer until the potatoes are very tender and breaking apart, 15 to 20 minutes. Drain well and return the potatoes to the hot pot for 1 minute, shaking gently, to steam off excess moisture.
  • Add the softened cream cheese, butter, and garlic powder to the hot potatoes. Mash with a potato masher (or beat with a hand mixer on low) until smooth — but don't overmix, or the potatoes turn gummy.
  • Beat in the sour cream and warm milk until the potatoes are creamy and fluffy. Fold in 1 cup of the shredded cheddar, then season with salt and pepper to taste.
  • Butter a 9x13-inch casserole dish and spread the mashed potatoes in evenly, smoothing the top with a spatula.
  • MAKE AHEAD: Let cool completely, cover tightly with plastic wrap (press it right onto the surface), and refrigerate for up to 3 days.
  • On serving day, let the casserole sit at room temperature for 30 minutes. Preheat the oven to 375°F (190°C).
  • Sprinkle the remaining 1 cup of cheddar evenly over the top. Bake uncovered for 35 to 40 minutes (45 to 50 minutes if baking straight from the fridge), until the cheese is melted and golden and the edges are bubbling.
  • Let rest 10 minutes, shower with chopped chives, and serve warm.

Notes

Start with cold water and salt it well — potatoes absorb flavor as they cook, and salting the water seasons them from the inside out.
Yukon Golds are the gold standard here: buttery texture and they mash up silky with almost no effort. Russets work too but need a touch more milk.
Room-temperature dairy is the secret to lump-free potatoes. Cold cream cheese and sour cream seize up against hot potatoes and leave streaks.
For the fluffiest texture, press plastic wrap right onto the surface of the potatoes before refrigerating — it prevents a dry skin from forming.
Customize the topping: swap cheddar for Gruyère or Parmesan, add crumbled bacon, or sprinkle buttery breadcrumbs over the cheese for crunch.
Reheat leftovers in a 350°F oven with a splash of milk stirred in — the microwave works in a pinch but can make them gluey.