1) Place potatoes in a large saucepan, add cold water just to cover and 1 tbsp of salt. Bring to a boil over high heat and cook until tender. Drain well and mash.
2) While the potatoes are cooking, combine the milk, garlic puree and butter in a small saucepan and bring to a simmer over low heat.
3) Stir the milk mixture into the potatoes until combined. Fold in the mascarpone and season well with salt and pepper.
4) Keep warm over in a bain marie or double boiler until serving.