Put an 8 oz package of softened cream cheese into your potatoes as you mash them, and you will be suprised at the results. You will not taste the cream cheese, but will just notice that the potatoes are creamier and richer than usual.
To about 5 pounds, more or less, of potatoes, use 1- 8 oz package cream cheese.
Then of course use a stick or so of real butter and then add milk or heavy cream, salt, pepper. Fresh chives would be excellent in these, too.