2) Meanwhile, in medium frying pan over a medium heat cook the bacon until crisp. Remove, drain on paper towels and chop.
3) Remove all but 2 tbsp of bacon grease from the pan and heat over a medium-high heat. Add the onions and saute for 2 minutes. Stir in the jalapenos and saute for 2 minutes more. Add the garlic and lightly saute for 1 more minute. Set aside to cool to room temperature.
4) Remove the potatoes from the oven and allow to cool to a workable temperature. Slice the potatoes in half lengthwise and use a spoon to scrape the flesh into a bowl. Add the butter to the bowl and pepper and salt to taste. Reserve 8 of the skin halves, discard the other 8.
5) Gently fold the onion, jalapeno and garlic mixture into the potato. Combine the horseradish, sour cream, half the pepper Jack cheese and the bacon; add to the potato mixture. Gently fold in the avocado.
6) Stuff the reserved potato skins with the mixture, top with the remaining cheese and place back in the oven on a baking sheet for 20 minutes. Serve hot.