Heat oven to broiler setting. Peel and cut potatoes into 1-inch pieces. Place potatoes and 1 teaspoon salt in a large pot and cover with water. Bring to a boil and continue to cook over medium heat until potatoes are tender, about 20 minutes more. Drain and return all but 1 cup of potatoes to the pot.
Mash the potatoes with a potato masher. Stir in the ricotta, milk, butter, remaining salt, and pepper to blend. Add the reserved potatoes and mash just until combined. Spoon 1/2 cup potatoes into 10 six-ounce ramekins and set on a baking pan. Place under broiler until browned. Serve hot