Combine first 7 ingredients in a blender, and process until smooth, scraping sides. Set aside.
Arrange bread slices in a single layer on a baking sheet. Sprinkle 1 1/2 teaspoons cheese on each bread slice. Broil bread slices 2 minutes or until lightly browned.
Combine lettuce and remaining ingredients in a large bowl. Drizzle buttermilk mixture over lettuce mixture; toss gently to coat. Serve with cheese toasts.