Make the Buttermilk-Chive Dressing: In small bowl, whisk buttermilk, mayonnaise, chives, vinegar, salt and pepper until smooth. Makes about 1/2 cup dressing.
Make the Salad: Arrange lettuce leaves in large bowl. Top with tomatoes, cheese and bacon. Serve with Buttermilk-Chive Dressing and baguette slices, if desired.