Place the potatoes in a large stockpot with enough water to cover. Salt lightly. Bring to a boil and cook for 10 to 15 minutes, or until there’s still a bit of bite to the potatoes.

Drain the potatoes and arrange them in a greased 3-quart casserole dish. Heat the oven to 350°.

In a medium bowl, combine the soup, milk, sour cream, cheese and onion. Add salt and pepper, to taste, and pour the mixture over the potatoes.

In a small saucepan, melt the butter over a low flame. Add the cornflake crumbs and stir until mixed.

Sprinkle over the casserole and bake, uncovered, for 30 to 45 minutes, until the crumbs are lightly browned and the potatoes are bubbling.