Place the garlic, green onions and pepper in a blender or the bowl of a food processor and pulse for a few times until puréed. Add the olive oil, vinegar, salt, pepper and water and as much of the lettuce and herbs as will fit and purée. Add the rest of the lettuce and herbs and continue to purée. Add additional cold water if needed to achieve a pourable soup-like consistency. Taste and adjust seasoning.
Place in the refrigerator to chill for an hour or until ready to serve. If the herbs have all floated to the top, just reblend briefly to combine.
Serve in small bowls or small glasses garnished with a couple or more of the optional garnishes, as desired. You can also set out bowls of garnishes and let each person garnish to taste.