The definitive "chopped salad," the Cobb was invented in Hollywood, at the Brown Derby restaurant, and quickly became an iconic American dish. At the Derby, it was always presented with its colorful mix of ingredients arranged neatly arranged, then tossed at the table.
Combine the vinegar, water, lemon juice, pepper, salt, Worcestershire sauce, and mustard in a blender and pulse briefly to combine. Stir in the olive and canola oil.
Chill for at least 4 hours in a sealed jar or bottle before using.
Arrange the iceberg, watercress, romaine, and chicory in 4 adjacent lines in the bottom of a wide, shallow wooden salad bowl. Arrange the tomatoes and chicken in alternating adjacent lines crosswise over the lines of greens. Sprinkle the bacon over the salad evenly. Arrange the avocado around the edges of the salad. Sprinkle the eggs, chives, and Roquefort evenly over the salad.
Just before serving, shake the dressing. Add 1 cup of the dressing and toss very well.