To make the potatoes:

Cup of Yum
1. Using a mandoline or a sharp chef's knife, slice the potatoes into 1/4-inch thick pieces. Rinse the slices under cold water, then store in a large bowl of water while slicing the remaining potatoes.
2. Drain potatoes. In a large saucepan over high heat, combine vinegar and 2 quarts water. Bring to a boil. 
3. Add potatoes and cook for 5 minutes. Drain well and spread in a single layer on rimmed baking sheets lined with paper towels. Dry five minutes.
4. In a Dutch oven, large pot, or deep fryer, heat oil to 400 degrees. Add 1/2 of potato slices and cook, stirring and flipping constantly with wire mesh spider or slotted spoon, until potatoes release no more bubbles, about 3 to 5 minutes (smaller chips may cook faster than large ones and should be removed from the oil as they finish).
5. Transfer potato slices to a rimmed baking sheet lined with paper towels, and sprinkle with salt. Repeat with remaining potato slices.

To make the nachos:

1. Preheat oven to 450 degrees. Transfer potato slices to a broiler-proof pie plate or serving platter.
2. Top with cheese and bacon. Bake until the cheese is hot and bubbly, about 3 minutes. Remove from oven and top with sour cream, tomato, scallions, and jalapeño slices, if using.