Chicken Salad Deluxe

1 1/4 cups prepared buttermilk salad dressing
1/2 cup mayonnaise
3 tablespoons half-and-half
1 3/4 teaspoons Beau Monde seasoning
1 teaspoon salt
1/2 teaspoon pepper
5 whole chicken breasts (about 2 pounds) skinned, cooked and cubed
10 ounces uncooked medium shell macaroni, cooked, rinsed, drained and cooled
3 cups diced celery
2 1/2 cups seedless green grapes, cut lengthwise into halves
1 package (12 ounces) slivered almonds
2 cans (2.25 ounces each) sliced water chestnuts drained
1/2 cup chopped onion

Combine salad dressing, mayonnaise, half-and-half, seasoning, salt, and pepper in small bowl; blend well. Cover refrigerate overnight to blend flavors. Combine chicken, shells, celery, grapes, almonds, water chestnuts and onions in large bowl. Pour dressing over salad; toss gently to coat. Serve on lettuce. Makes 20 servings.