In a large pot, cover the potatoes with water, add 1 tablespoon salt, and bring to a boil. Cover and cook for 20-30 minutes, until a knife inserted into a potato meets no resistance. Drain. When cool enough, cut each potato in half. Cut each half into ¼ inch slices and put in a large bowl. Sprinkle with 3 tablespoons of the cider vinegar and toss in the red onion, green onions and parsley.
In a heavy pan, heat the olive oil over medium-high heat. Add the sausage and cook until it begins to brown, about 5 minutes. Remove with a slotted spoon and add to the potatoes. To the fat remaining in the pan, add the garlic, cayenne, mustard, black pepper, Tabasco and remaining 3 tablespoons of cider vinegar. Bring to a boil whisking constantly. This should loosen any sausage bits and produce a smooth creamy dressing. Salt to taste. Pour the dressing over the sausages and potatoes, and mix lightly. Serve immediately.