Arrange lettuce, chicken, vegetables, cheese, pepproni, olives, and basil in salad bowls or plates. (Alternatively, toss the ingredients together in one large serving bowl.)
Whisk together olive oil, vinegar, mustard, garlic, Italian seasoning, and salt and pepper. Adjust seasoning as needed. (Whisk in sour cream if you want a creamy dressing.)
Drizzle dressing over salads or toss dressing to distribute into salad in serving bowl.
Top with any garnishes or crunchy additions desired-- croutons, French-fried onions, nuts, extra herbs, etc., and serve.
For a build-your-own salad, lay everything out and let people construct their own salads! This is great for families with varying preferences, guests whose preferences you don't know about, or groups with varied special diets.