01 - Melt butter in a large skillet over medium heat. Add diced onions, garlic, salt, pepper, and sugar. Sauté, stirring often, until onions are deeply golden and caramelized, about 25–30 minutes. Let cool to room temperature.
02 - In a medium bowl, whisk together sour cream, mayonnaise, softened cream cheese, Worcestershire sauce, and cayenne pepper (if using) until smooth and fully incorporated.
03 - Fold in the cooled caramelized onions and half of the chives. Mix well to distribute the onions evenly throughout the cream base.
04 - Cover the bowl and refrigerate at least 1 hour for flavors to meld and the dip to thicken slightly.
05 - Transfer to a serving bowl, garnish with remaining chives, and serve with sturdy potato chips or kettle chips for dipping.