Combine the first 7 ingredients in a small bowl. Cover and store in the fridge until needed. Preheat the oven to 425 degrees F. Line a large baking sheet with parchment paper. Cut each potato, lengthwise, in half. Cut each half potato, lengthwise, into 4–5 wedges. Place the potatoes in a bowl. Add the oil, lemon zest, paprika and salt and white pepper to taste and toss to coat. Arrange the potatoes on the baking sheet. Roast the potatoes 20 minutes. Turn each potato over and roast 10 minutes more, or until golden and crispy. Arrange the potatoes on a platter with the mayonnaise alongside for dipping.