Preheat the oven to 425 degrees.
Scrub the potatoes very well with a vegetable brush. Using a fork, poke each 5 times. Rub the outside of each with 1/4 teaspoon olive oil. Place them directly on an oven rack and bake them for approximately 50 minutes to 1 hour or until tender through. Let them cool for 1-2 hours or refrigerate them in a re-sealable plastic bag for up to 1 day.
Cut the potatoes in half lengthwise. Using a spoon, carefully scrape out the centers of the halves, leaving an even 1/2 inch thick potato shell in tact.
Spray a medium, non-stick baking sheet with olive oil spray. Arrange the potato shells on the baking sheet, so they barely touch. Lightly spray the tops with olive oil spray then sprinkle them evenly with the garlic, cayenne, and salt. Bake them for 10 minutes.
Meanwhile, place a small, non-stick frying pan over medium-high heat. Add the bacon and cook it, stirring frequently until barely crisped, about 3-5 minutes. Transfer the bacon to a medium shallow bowl lined with a paper towel to drain.
Then sprinkle the cheese, bacon, then chives evenly over the baked shells. Bake them for an additional 15-18 minutes more or until the potatoes are lightly browned. Top with sour cream if using. Serve immediately.