1. In a small bowl, whisk together the vinegar, lime zest, lime juice, shallot, brown sugar, mustard, paprika, salt, and pepper.
2. Whisk in the oil until emulsified.
3. Place the sweet potatoes in a steamer basket set over a pot filled with a couple inches of simmering water.
4. Cover and steam until tender when poked with a knife or fork, about 15 minutes.
5. Transfer the sweet potatoes from the steamer to a large bowl and while still hot, pour the dressing over the sweet potatoes and toss to coat.
6. Stir in the celery and chives and serve with the bacon, if desired, and a little paprika and chives sprinkled on top.
7. Let cool slightly and serve warm, or cool completely and serve at room temperature.