Fry the bacon until crisp and drain on paper towels. Crumble the bacon and set aside. Reserve 2 tablespoons of the bacon fat in the frypan.
In a saucepan place the sweet potatoes and 2 teaspoons salt and cover with water. Bring to a boil, reduce heat and cook, uncovered, until the sweet potatoes are tender, about 25 minutes. Drain, and cut into thin slices when cool enough to handle.
Lay the sweet potato slices in layers on a warm platter. Sprinkle with bacon, onion, celery, parsley and chives.
Reheat the frypan with the bacon fat. Add the balsamic vinegar and deglaze the pan, scraping up any burned bits. Add the chickens tock, red wine vinegar, sugar and salt and pepper to taste. Bring to a boil then drizzle over the sweet potatoes. Serve immediately.