Fill a large pot with cold water. Place in the potatoes and flavour the water with salt. On high heat bring the water up to a boil and poke with a knife to check if the potatoes are cooked. The knife should be able to slide into the potato easily. Once they are cooked drain the potatoes.
In the same pot add in the butter, Mascarpone cheese, Parmigiano Reggiano, roasted garlic, chives, parsley, salt and pepper. If the potatoes are too thick simple add some chicken stock to loosen them up.