2 tablespoons butter
1 large onion, sliced
Salt and ground pepper
2 to 3 heads romaine lettuce, cut into thin ribbons
2 cups chicken stock
1/2 to 1 cup cream or half-and-half
Small croutons or crumbled bacon for garnish
Put butter in a medium saucepan over medium heat; when it melts, add onion and sweat for about 2 minutes or until it begins to soften; sprinkle with salt and pepper. Add all but a couple of handfuls of the lettuce to the pan, reserving the rest for garnish, and cook until it wilts. Add stock, turn the heat to medium-high and bring liquid to a boil; lower heat to medium and cook until lettuce is very soft, about 5 minutes.
Put cooked lettuce in a blender and add 2 cups of ice water. Pur?e mixture until smooth, then put in a large bowl and refrigerate for at least an hour.
Once soup is chilled, add cream or half-and-half to taste and sprinkle with salt and pepper. Finely chop reserved lettuce and put about 1/4 cup in each bowl and ladle soup on top. Garnish with croutons or bacon.