Place the diced potatoes in a saucepan, submerge them in cold water, and set the pot over high heat. Once boiling, reduce the heat to a gentle simmer and cook for 7–9 minutes, until the potatoes are tender and can be easily pierced with a fork.
Once cooked, drain the potatoes thoroughly and allow them to cool completely at room temperature.
Transfer the cooled potatoes to a large mixing bowl. Add the finely chopped onion, mayonnaise, salad cream, white pepper, and salt.
Mix all components together gently but thoroughly, ensuring each piece of potato is evenly coated in the creamy mixture. Adjust seasoning to taste, if needed.
Cover the bowl and refrigerate the salad for at least 30 minutes, or up to 24 hours before serving.
When ready to serve, garnish the top with chopped chives and a light sprinkle of black pepper, if desired.