For dressing, in a blender combine lemon juice, 3 anchovy fillets, and 3 cloves garlic. Cover and blend until mixture is nearly smooth, stopping to scrape down sides as needed. Add oil, hard-cooked egg yolk, mustard, and sugar. Cover and blend until smooth. If desired, cover and chill for up to 24 hours.
Rub the inside of a wooden salad bowl with cut sides of 1 clove garlic; discard garlic. In the salad bowl combine lettuce, chicken, Parmesan Croutons, and, if desired, cherry tomatoes. Pour dressing over lettuce mixture; toss gently to coat. Sprinkle with cheese; toss gently to combine. If desired, add additional anchovy fillets. Sprinkle each serving with pepper.
Preheat oven to 300 degrees F. Cut bread into 1-inch cubes (you should have about 3-1/2 cups); set aside. In a small saucepan melt butter. Remove from heat. Transfer to a large bowl. Stir in Parmesan cheese and garlic. Add bread cubes, stirring until cubes are coated with butter mixture. Spread bread cubes in a single layer in a shallow baking pan or on a baking sheet. Bake for 10 minutes; stir. Bake about 10 minutes more or until bread cubes are crisp and golden. Cool completely; store in an airtight container for up to 24 hours.