Cook bacon in a large, heavy skillet over medium until crisp, about 15 minutes. Transfer to a plate lined with paper towels. Reserve 1 tablespoon of the drippings in skillet; transfer 2 tablespoons of the drippings to a small bowl. Dice bacon, and set aside.
Add leeks to skillet, and cook, stirring often, 3 minutes. Combine leeks and Brussels sprouts in a large bowl.
Add olive oil, apple cider vinegar, honey, salt, and pepper to reserved 2 tablespoons of drippings, and whisk to combine. Add to Brussels sprouts and leeks; toss to coat. Stir in chopped pecans, chives, and diced bacon. Serve immediately.
