Scrub the potatoes, peel them if desired, and cut them into roughly 1 1/2-inch chunks. If using very small potatoes, halve them instead, keeping the pieces as uniform as possible.

Set the Instant Pot to Sauté and cook the chopped bacon for 5 to 7 minutes, stirring occasionally, until browned and most of the fat has rendered. Leave about 2 tablespoons of bacon fat in the pot.

Add the diced onion and sauté for 2 to 3 minutes, until softened. Turn off Sauté, pour in the broth, and scrape the bottom thoroughly to loosen every browned bit.

Add the potatoes and lock the lid. Set the valve to Sealing and cook on High Pressure for 4 minutes.

Allow a 5-minute natural release, then carefully quick-release the remaining pressure. Open the lid once the pin drops.

Transfer the potatoes and bacon to a serving bowl, leaving the cooking liquid in the Instant Pot. Handle the potatoes gently so the pieces stay intact.

Stir the apple cider vinegar, sugar, Dijon mustard, kosher salt, and black pepper into the hot cooking liquid. Turn on Sauté and simmer for 2 to 4 minutes, until the dressing is slightly reduced.

For a thicker dressing, whisk in the cornstarch slurry and simmer briefly until the sauce thickens. Pour the hot dressing over the potatoes and bacon, then gently fold everything together.

Sprinkle with chopped parsley or chives and serve warm. Taste before serving and add a little more salt or pepper if needed.