In a large, heavy-bottomed skillet, warm the olive oil and place the escarole in the skillet, adding water to come halfway up its sides. Cover, bring the liquid to a boil, reduce to a simmer and cook 15 minutes. Turn the escarole gently with tongs and cook another 10 minutes, until the water has evaporated and the escarole is soft. Uncover and cook for another 5 minutes, to brown the escarole. Cut the string, slice into 4 portions and serve.