Scrub potatoes and cut in half.(You can peel them or not, your preference.) Place in large stockpot and cover with water. Add about 1 Tbsp salt. Bring to boil and keep at medium boil for approx. 30 min, or until potatoes can be easily pierced with a sharp knife. Drain and let cool so you can handle them easily. When cooled sufficiently to handle, chop them into medium dice and reserve in a bowl til needed.
In the same stockpot, saute the cut up bacon until browned and somewhat crispy. Remove the bacon and drain all but 2-3 Tbsp of bacon fat. Place pot back on stove and add onion and celery. Fry until softened and just starting to brown, stirring occasionally. Add vinegar, sugar, celery seed, pepper and half the salt to the sauteed vegetables. Simmer together until sugar is dissolved, 3 to 5 minutes. Add 2/3 of the bacon bits to the sauce. Mix the cornstarch with the water and add to the pot, cooking at just boiling until sauce thickens slightly. Add the diced potatoes and mix gently. Taste and adjust salt and other seasonings. Spoon into casserole or serving bowl and serve while warm with reserved bacon bits and chopped parsley on top. To serve later, cover and refrigerate until just before serving. When ready to serve, either microwave until hot, or place in a 350° oven for 20 minutes covered with foil until hot. Serve with remaining bacon and parsley sprinkled over the top if desired.