Prepare the sauce: Mix the sauce ingredients together in a small bowl and set aside. The sauce can be made several days ahead, covered, and refrigerated.
For the salad: Preheat the oven to 425℉, and greaser spray a large, rimmed baking sheet (or line with parchment paper for easier cleanup). Chop the potatoes into bite-size pieces. (No need to peel.) Toss with the olive oil, salt, and pepper. (I use about ½ teaspoon each salt and pepper.) Spread the potatoes evenly over the prepared baking sheet. (Helpful hint: when using, I place the sweet potatoes on one side of the baking sheet as they are often done 5+ minutes before the new potatoes.)
Roast the potatoes for 25-30 minutes or until tender, checking and turning after 20 minutes. Again, if using sweet potatoes, you’ll likely be able to slide them into a bowl after 20 minutes or so, allowing the remaining potatoes to finish cooking.
Transfer the cooked potatoes to a large bowl and allow them to cool slightly. Then add the celery, onions, parsley, and optional ingredients of choice. (Helpful hint: If making the salad in advance and using optional bacon, I like to add when serving to maintain crispness.) Drizzle with dressing and toss to evenly coat.
Note: Depending on how well coated you like your salad, you may not use it all. If you have a little leftover, cover, and store for use as a dip, sandwich spread, etc. The sauce will add flavor to basic potatoes, rice, oven fries, and more.
Serving and storage: The salad may be served warm, room temperature, or cold. Leftovers are delicious and will keep in the refrigerator for about 5 days.