INGREDIENTS
3 tbsp
Chives
1
Spanish onion, large
4
lbs Yukon gold or other waxy potatoes
2 tbsp
Mustard, whole-grain
1 pinch
Cayenne pepper
1
Kosher salt and freshly ground black pepper
1/4 cup
Cider vinegar
¼ cup, plus 1 tablespoon, olive oil, divided