1. Combine chicken, pineapple, cheese and tomatoes.
2. Add salt and pepper to taste.
3. Mix sour cream with yellow mustard and toss with the chicken mixture.
4. Chill in the refrigerator.
5. Just before serving, toss in the lettuce and sprinkle peanuts on top.

Note:
If sour cream is not available, drain 2 cups of fresh curds through a thin cloth, beat till smooth and use in the recipe.