2. Place half of the oil or butter, lemon zest, water, and escarole in a 3-quart sauté pan or 12-inch skillet. Sprinkle with salt. Cover and set on medium heat. As soon as the water begins to steam, uncover, then stir every 10 seconds or so until all of the leaves are uniformly wilted and vibrant, glistening green. If the water evaporates before the leaves are cooked, add a few more drops at a time, just enough to keep the escarole from frying. The bright flavor and texture depend on quick cooking in even, steamy heat, not boiling water.
3. Remove the shiny cooked leaves to hold on a warm plate while you cook the second batch. Add the remaining butter or oil, lemon zest, escarole, and water as needed. Cook as described above. Serve promptly, spooning the syrupy oil or butter that remains in the pan over the leaves. If the liquid is watery, not syrupy, raise the heat and simmer until it has some body.
Adam Rapoport, editor in chief of Bon Appetit magazine and the website www.bonappetit.com, knows his way around a grill. He has edited an entire book on the subject: The Grilling Book: The Definitive Guide from Bon Appetit.