Kosher salt
¼ cup cup olive oil, plus more for drizzling
1 small red onion, thinly sliced
¼ cup apple cider vinegar
1 tablespoon whole grain mustard
1 teaspoon Old Bay seasoning
1 teaspoon (or more) coarsely ground black pepper
Pinch of cayenne pepper
2 cups kettle-cooked potato chips
¼ cup coarsely chopped parsley
3 tablespoons finely chopped chives
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. 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. 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.