Preheat the oven to 200°C (400˚F) Wrap the potatoes in aluminum foil. Place the potatoes on the rack and roast for 45 minutes, or until the tip of a sharp knife slides easily through the thickest part of the potato. Larger potatoes may take longer.
Mix the cream cheese with the mascarpone, herbs, garlic and lemon. Season to taste with salt and pepper.
Place the potatoes on a platter and slice the tops of the potatoes with a sharp knife. Gently press the sides of the potatoes with your fingers to break the skin.
Spoon a generous amount of the herb cream cheese over the top and sprinkle with more chives and lemon zest.