Drop the garlic halves through the opening in a blender lid with
blender on; process until minced. Add mayonnaise and the next 5
ingredients (mayonnaise through pepper); process until well-blended.
Cover and chill at least 1 hour. Combine oil, Cajun seasoning, and
minced garlic in a medium microwaveable bowl. Microwave on High for
20 seconds. Add bread cubes; toss gently to coat. Spread bread cubes
in a single layer on a baking sheet; bake at 400F for 15 minutes or
until golden brown. Place lettuce in a large bowl. Add dressing; toss
gently to coat. Sprinkle with cheese and top with croutons.