Mashed Potato Casserole

by Bhagya

Purists beware! This mashed potato casserole is delicious and can be made ahead. When you want mashed potatoes on the menu but have enough to do on the day, try this!

230 grams unsalted butter, softened, and more for the pan
3 kg potatoes, peeled and cut into chunks
2 tablespoons plus 1 teaspoon salt
1½ cups sour cream
1 teaspoon black pepper
1/3 cup finely chopped chives
⅔ cup bread crumbs
⅔ cup grated Parmigiano-Reggiano cheese

Lightly grease a 33 x 23 cm baking pan
In a large pot, bring the potatoes, 5 litres water and 2 tablespoons salt to a boil. Boil potatoes until fork tender, about 20 minutes. Drain.
Reserve 4 tablespoons of the butter and mash potatoes with the rest plus sour cream, 1 teaspoon salt,and pepper. Mash in the chives. Taste and adjust seasoning, if necessary. Spread potatoes into the prepared pan. Cover and refrigerate for up to three days.
In a small bowl, combine the remaining butter, breadcrumbs and cheese. Mix together until it forms coarse crumbs. Crumbs can be refrigerated for three days.
Heat the oven to 200 ºC degrees. Sprinkle crumbs over the top of the potato casserole and bake until golden and crisp, 30 to 40 minutes.