Make-Ahead Mashed Potato Casserole
A stress-free, creamy mashed potato casserole with a crispy parmesan breadcrumb crust. Perfect for holidays, potlucks, and weeknight dinners!
Ingredients
Potatoes
- 6 lbs Yukon Gold potatoes peeled and cut into even chunks
- 2 tbsp kosher salt for boiling water
- 10 tbsp unsalted butter softened at room temperature
- 1 1/2 cups sour cream full fat preferred
- 1 tsp kosher salt for the mash
- 1 tsp black pepper freshly ground
- 6 tbsp chives finely chopped
Crispy Topping
- 4 tbsp unsalted butter softened
- 2/3 cup plain bread crumbs unseasoned
- 2/3 cup Parmigiano-Reggiano freshly grated
Instructions
- Grab a 9x13-inch baking dish and grease it well with extra softened butter. Coat the bottom and all four sides. Set it aside.
- Place the peeled, chunked Yukon Gold potatoes in a large pot and cover with about 4 quarts of cold water (water should sit about an inch above the potatoes). Add 2 tablespoons of kosher salt. Bring to a rolling boil over high heat and cook until fork-tender, about 20 minutes.
- Drain the potatoes in a colander, giving it a few good shakes to remove excess water. Return the hot potatoes to the empty pot and let them sit off the heat for two full minutes to dry out.
- Add 10 tablespoons of softened butter, sour cream, 1 teaspoon of kosher salt, and black pepper to the pot. Mash with a sturdy hand potato masher until smooth and creamy. Gently fold in the chopped chives. Scoop the mash into your greased baking pan and spread into an even layer.
- In a small bowl, combine 4 tablespoons softened butter, bread crumbs, and Parmigiano-Reggiano. Mix with your fingers until the butter is evenly distributed and it looks like coarse, damp sand.
- Preheat your oven to 400°F. Sprinkle the crumb mixture evenly over the surface of the potatoes. Bake on the middle rack for 30 to 40 minutes, until the topping is deeply golden and crispy.
- Set the casserole on a wire rack and let it rest for at least 10 minutes before serving to help it set up.
Notes
Make-Ahead Tip: Assemble the potato layer up to three days ahead. Cover tightly with foil and refrigerate. Store the crumb topping separately. When baking from cold, bake covered at 400°F for 40 minutes, then remove foil, add topping, and bake another 20 to 30 minutes.
Freezing is not recommended as the sour cream tends to separate and become grainy.