Bake potatoes in their skins then peel Chop or grate coarsely Combine cheese and only 4 tablespoons butter in large saucepan Heat stirring constantly until cheese and butter melt Remove from heat and blend in sour cream onion salt and pepper Fold in potatoes and spoon into a greased 2-quart casserole dish Dot with remaining 2 tablespoons of butter Cover and bake at 300 for 25 minutes or until bubbly If made ahead and refrigerated bake longer about 40 to 45 minutes Great with tenderloin Serves 6 to 8 Can do ahead