Ode to watercress, the oft overlooked lettuce that deserves to be up there with arugula as a go-to green for making salads and soups, such as this one. It has a similar peppery flavor but is very distinctive in its own right, with tendrils that are sturdy enough to hold up to cooking, yet the leaves are tender and sprightly at once. Here the cress is added to a pureed vegetable soup made with carrots and pumpkin.