Cheesy Mashed Potatoes Casserole

4.92 from 56 votes

A savory make ahead cheesy mashed potato casserole that's easy to double or triple, making your holiday cooking to-do's a whole lot easier!

Prep Time20

Cook Time35

Total Time55

Course: Side Dish

Cuisine: American, Southern

Servings: servings

Author: Jenny DeRemer

Cost: $0.87 per serving

Equipment

8 x 8-inch or 9 x 9-inch casserole dish

Ingredients

4 pounds russet potatoes
Kosher salt for salting the potato water
2 tablespoons chives fresh, chopped
1 bunch scallions chopped, white and green parts separated
½ cup + 2 tablespoons unsalted butter divided; 1/2 cup melted, 1 tablespoon softened to grease baking dish, 1 tablespoon cut into tiny pieces
* 4-5 tablespoons whole milk * OPTIONAL
1 cup sour cream brought to room temperature
1 cup sharp cheddar or white cheddar cheese divided; may substitute any melty cheese if desired

Instructions

If planning to bake immediately, preheat oven to 350°F. Butter an 8 x 8-inch or a 9 x 9-inch oven-safe dish with 1 tablespoon of butter. Set aside.
Peel and quarter the potatoes and add them to a large stock pot or Dutch oven. Add enough COLD tap water to cover by 1/2-inch. Sprinkle with Kosher salt, about 1/2 tablespoon.
Bring the pot to a boil and boil the potatoes for about 15 minutes or until a fork stabs without resistance. Drain the potatoes and return to the pot. Place the pot back over the still-warm burner and shake to evaporate excess water.
Melt 1/2 cup of the butter. Using a hand mixer or a potato masher, add to the potatoes and mash coarsely. Alternatively, run through a potato ricer. They need not be smooth yet. Add the sour cream. Now mash until smooth. DO NOT overwork the potatoes. If they feel too stiff, you may add a splash of milk, about 4 to 5 tablespoons, however completely optional.
Fold the chopped chives, the green parts of the scallions, and 3/4 cup of the shredded sharp cheddar cheese. Spoon the mixture into the prepared casserole dish. Scatter the remaining white parts of the scallions over the top, along with additional freshly cracked black pepper and the remaining 1/4-cup cheese. Dot the remaining tablespoon of butter over the top of the casserole.

You can bake the casserole now or cover it and refrigerate for a later bake.

To bake the casserole immediately, place into the preheated oven and bake for 20 minutes or until the top is lightly golden, the cheese melts, and scallions begin to brown and char.
If baking the casserole later, pull it from the refrigerator and let it stand while the oven preheats. Place into the oven and bake for 30 to 35 minutes or until lightly golden and scallions begin to brown and char.

Notes

To Freeze:

For a whole casserole, assemble the recipe following the directions, stopping just before baking it. Assemble in a freezer-safe glass baking dish with a tight-fitting lid or a double layer of aluminum foil. After marking the contents and the date of freeze on the outside, place them flat into the freezer. Freeze for up to three months.

For freezing leftover portions which have already been baked, spoon into a freezer-safe plastic container with a tight-fitting lid, then mark with the contents and date of freeze noted on the container. Freeze for up to three months.

To thaw and heat:

Place in the refrigerator overnight.

To heat a whole casserole, once wholly thawed, bake as directed on the recipe card, as it will be being baked for the first time.

For previously baked portions, heat gently in the microwave until hot.

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