Step 1

Place potatoes in a large pot and pour in cold water to cover; season with salt. Bring to a boil; reduce heat and simmer until tender, 15–18 minutes. Drain and return to pot to dry out; let cool.

Step 2

Meanwhile, heat ¼ cup oil in a medium skillet over medium-high. Add onion; season with salt. Cook, stirring occasionally, until soft, about 5 minutes.

Step 3

Transfer onion to a large bowl. Stir in vinegar, mustard, Old Bay, black pepper, and cayenne. Add potatoes, potato chips, parsley, and chives to vinaigrette and toss to combine. Taste and season with salt and black pepper if needed; drizzle with more oil.

Step 4

Do Ahead: Vinaigrette can be made 3 days ahead; cover and chill.