Peel and cut the potatoes into chunks. Place in a pot, cover with water, add salt, and boil until completely soft, about 15-20 minutes. Drain thoroughly and mash until smooth. Let cool slightly.

To the mashed potatoes, add 2 eggs, grated carrot, chopped parsley, salt, and sweet paprika. Mix well. Add cornstarch and flour, mixing until you have a soft, pliable dough. Set aside.

Cut chicken fillets into small cubes. Heat vegetable oil in a large pan over medium-high heat. Cook the chicken until golden and cooked through. Remove and set aside.

In the same pan, add more oil if needed. Sauté diced onion until translucent. Add sliced mushrooms and cook until they release their moisture and become golden. Add minced garlic and cook for 1 minute.

Return the cooked chicken to the pan with the mushrooms and onions. Season with Italian herbs, black pepper, nutmeg, and salt. Pour in the cream and stir well. Cook for 2-3 minutes until the mixture thickens slightly. Remove from heat and stir in shredded mozzarella cheese until melted. Let the filling cool completely.

Divide the potato dough into 2 equal portions. Roll out one portion into a circle about 1cm thick. Place spoonfuls of the cooled filling on the dough. Roll out the second portion of dough and place it over the filling. Seal and cut into individual patties.

Set up a breading station with flour, beaten eggs, and breadcrumbs. Dip each patty in flour, then beaten egg, and finally coat with breadcrumbs.

Heat vegetable oil in a skillet over medium heat. Fry the patties until golden brown and crispy, about 3-4 minutes on each side. Drain on paper towels.

For the sauce, combine sour cream, mayonnaise, minced garlic, chopped dill, and salt in a small bowl. Mix well and refrigerate until serving.