In a large sauce pan combine the potatoes and salt. Cover with water, bring to a boil over high heat and then reduce to a simmer and cook until the potatoes are easily pierced with a fork. about 5-6 minutes.
Reserve 1/4 cup cooking water to add to the dressing, and discard the rest. Transfer the potatoes to a large mixing bowl.
In a food processor combine all the remaining ingredients, including the 1/4 cup reserved water, but excluding the pepper and emulsify.
(The water absords starch from the potatoes and adds thickness and creaminess to the dressing).
Add the dressing to the potatoes and give it a good toss. Let the salad sit for a couple minutes and toss again. Add salt and pepper to taste.
Serve immediately, or cover and place in the fridge for 2-3 days.