These are my absolute favorite mashed potatoes! I usually use red potatoes, but I don't know the exact amount. I kind of eyeball it. I like it better with the baking potatoes, but my boyfriend prefers the red ones.
Place hot potatoes into a large bowl. Start mixing the potatoes at medium speed until they are smooth. Add sour cream, cream cheese, butter, milk, garlic, salt, and pepper and continue beating until thoroughly mixed.
Pour into a greased 9x13-inch baking dish. Bake, uncovered, for 30 min at 400ºF.