Place the potatoes in a large pot and add 2 tsp salt and enough cold water to cover. Bring to a boil. Reduce heat and simmer until the potatoes are very tender, 20 to 25 minutes. Drain and return the potatoes to the pot.
Add the Parmesan, ricotta, milk, butter, 1/2 tsp salt, and 1/4 teaspoon cracked pepper to the potatoes and mash to the desired consistency.