Peel potatoes and cut into cubes. In a large pot of cold salted water, boil potatoes for 15 minutes until fork tender. Do not overcook! Drain and transfer into a large mixing bowl. Add the butter, milk, salt, pepper, sour cream, and cream cheese. Mix with a hand mixer until blended together and lump free. Stir in chopped onion and cheddar cheese.
Place into an ovenproof casserole dish and garnish top with extra cheese. Bake at 325°F/163°C for 35–40 minutes. If reheating, remove from refrigerator 1 hour before heating.
Bake covered for 40-60 minutes until center is hot. Remove cover for 10 minutes to let top brown lightly.
Peel potatoes and cut into cubes. In a large pot of cold salted water, boil potatoes for 15 minutes until fork tender. Do not overcook! Drain and transfer into a large mixing bowl. Add the butter, milk, salt, pepper, sour cream, and cream cheese. Mix with a hand mixer until blended together and lump free. Stir in chopped onion and cheddar cheese.
Place into an ovenproof casserole dish and garnish top with extra cheese. Bake at 325°F/163°C for 35–40 minutes. If reheating, remove from refrigerator 1 hour before heating.
Bake covered for 40-60 minutes until center is hot. Remove cover for 10 minutes to let top brown lightly.
