Peel potatoes and boil in enough water to cover until tender. Let cool. Cut into chunks.
To make dressing, put lemon juice, half of parsley, green onions and mint in blender. Blend. Drizzle in olive oil while blender is on. Season to taste with salt and pepper. Adjust amount of lemon juice and olive oil to taste.
Combine potatoes and remaining parsley, green onions and mint in a bowl. Add dressing and toss to coat. Season with more salt and pepper. Chill well.