The creamy texture of these mashed potatoes is achieved without using cream or milk. The secret is to use the cooking liquid to moisten the puree, adding just a small amount of butter or olive oil to provide a luxurious finish. Top them with this rich gravy that can be made with fresh shiitakes as well as portobellos. Leave the mushroom pieces in for a chunky-style sauce or strain them out for a velvety consistency.
Make Ahead Tip: Keep the potatoes hot, covered with parchment or wax paper, over a pan of barely simmering water for up to 1 hour.
