5 lbs (2.25kg) yellow fleshed potatoes, peeled and cut into 1½ inch (4cm) chunks
½ cup (113g) unsalted butter, cubed, room temperature, divided
1 brick (250g) cream cheese, cubed, room temperature
1 cup (250g) sour cream
Freshly ground black pepper
2 cups (100g) crushed flaked corn cereal
2 cups (250g) grated medium cheddar cheese
Spray a 2L casserole dish with cooking spray. Heat oven to 350F (176C).
Place potatoes in a large saucepan covered with 1 inch (2½ cm) of water. Season water liberally with salt and bring to a boil over high heat.
Cook potatoes until very tender, about 15 to 20 minutes. Drain and return to pan and mash. Add 1/3 cup (75g) butter, cream cheese and sour cream. Beat with a hand mixer until fluffy. Season with salt and pepper to taste. Spoon into prepared dish and spread evenly to edges. Sprinkle with cereal and cheese and dot with remaining butter.
Bake until cheese is melted and edges are beginning to brown, about 35 minutes.