Peel and quarter potatoes. Heat water and 2 teaspoons salt of the salt in a Dutch oven over high heat until boiling. Add potatoes, cover and cook until mixture returns to a boil. Reduce heat to low and cook 20-25 minutes, or until potatoes are tender. Drain potatoes; return to Dutch oven, away from heat. Mash potatoes with a potato masher until smooth. Add butter, mascarpone, chives, remaining salt and the pepper; mix until smooth. Gradually add enough of the warmed milk to make potatoes creamy and fluffy, mixing well after each addition. (At this point, potatoes may be stored in containers and refrigerated for a couple days.) Spread potatoes into a buttered, large baking dish or pan, or divide between 2 dishes or pans. Dot with butter and sprinkle with paprika. Bake at 350 degrees about 45 minutes or until hot.