Make dressing: Puree mayonnaise, sour cream, vinegar, minced garlic, anchovies, lemon juice, Worcestershire sauce and mustard in blender until smooth. With motor running, drizzle in 1/2 cup oil and blend. Season lightly with salt and pepper. Cover and refrigerate.
Preheat grill to medium-high. Brush cut side of bread with some of remaining oil. Grill bread, turning once, until toasted, 3 to 5 minutes. Remove bread from grill and rub with cut side of halved garlic clove. Cut into 1-inch pieces.
Brush all sides of lettuce with remaining oil; sprinkle with salt and pepper. Grill lettuce, turning frequently, until lightly charred around edges, 2 to 3 minutes.
Chop lettuce and divide among 6 bowls. Sprinkle with Parmesan, scatter baguette pieces over and drizzle with some of the dressing. Serve immediately, passing additional dressing on the side.