Scrub potatoes and quarter them and drop into a kettle of cold salted water. Bring to a boil, and cook until tender but still firm about 8-10 minutes after water reaches boil.
Meanwhile, chop the bacon and saute in a small skillet until crisp. Remove bacon and reserve.
In the bacon fat, saute chopped shallots until tender but not at all brown, about 5 minutes or so. Reserve shallots and fat.
When the potatoes are done, drain them and drop them into a mixing bowl.
Pour vinegar, olive oil, shallots, and reserved bacon fat over the still hot potatoes. Season with salt and pepper to taste, and gently toss. Add purple onion and parsley and toss again. Cool to room temperature, cover and refrigerate.
Before serving bring back to room temperature, toss, correct seasonings, and add additional oil and vinegar, if the salad seems dry. Sprinkle reserved bacon on top.