Scrub potatoes well, pierce a few times with a fork and bake until soft, either approximately 10 minutes in the microwave or one hour in a 350 degree oven. Cool for 10 minutes.Cut the tops off of the potatoes lengthwise and discard. Carefully scoop the cooked potato out of each potato skin, leaving the skins as intact as possible.Mash all the potato insides with cream cheese and butter. Add half and half in small increments until the potatoes are a consistency that you like (you might not need all the half and half). Stir in the taco season until well-mixed, and then stir in the chicken if you are using it.Sprinkle cheese on the top of each potato. Place the potatoes on a baking sheet and bake in a 350 degree oven for about 10 minutes or until cheese is melted.Garnish with your choice of toppings and serve at once.