Boil the potatoes in salted water until fork tender, drain and mash the potatoes. (About 25 Minutes)

Stir in the salt, melted butter and mozzarella cheese, cover and set aside.

In a large mixing bowl, whisk together the water, heavy cream, sour cream, vegetable oil, egg and salt.

Mix in the flour 1 cup at a time until fully incorporated.

Using clean hands, knead the dough in the bowl for 4-5 minutes until smooth and elastic, add in more flour if needed 1 tablespoon at a time.

Cover and let rest for 30 minutes.

Cut the dough in half and shape both halves into balls.

On a lightly flour surface roll out one half of the dough using a lightly floured rolling pin until about ⅛” thick.

Use a 3” round cookie cutter, remove the scraps and set aside to roll out later.

Add 2 teaspoons of the mashed potato mixture to the middle of each dough round, pull the edges together and pinch to seal tightly. Crimp the edges with your fingers or using the tines of a fork. Repeat this process until you’ve used up the dough and mashed potato mixture.

Bring a large pot of salted water to a boil, add 10 fresh pierogies to the boiling water and cook until they begin to float, remove with a slotted spoon and repeat with the remaining pierogies. (the pierogies can be garnished and eaten at this point) The pierogies must be boiled before pan frying.

To pan fry the pierogies, melt one tablespoon butter over medium heat and fry the pierogies for 3-4 minutes on both sides or until lightly golden brown. Cook in batches.

Serve the pierogies with sour cream, melted butter and sliced green onion, enjoy!