Gather all ingredients and equipment needed.
In a pot, pour enough water to cover pierogis and boil, then add pierogis and cook until done about 2-3 minutes or refer to manufacturer's instructions. Se aside.
Preheat oven to 350°F and heat pot roast until internal temp is 120°F. Tear or slice apart small chunks.
To make mushroom gravy, in a frying pan or skillet on medium heat, add olive oil, shallots, garlic and saute slightly. Then add mushrooms and cook until mushrooms are slightly browned. Then add chicken stock, and using a wooden spoon or spatula, mix ingredients together making sure you slowly scrape bits stuck to the bottom of the pan for extra flavor which is called, "fond". Let simmer and reduce until the sauce coats the back of the wooden spoon or spatula. Turn off heat and add heavy cream, salt and black pepper, and mix until fully combined. Cool slightly and taste.
To assemble, place pierogis on a platter and top with chunks of pot roast, then pour mushroom gravy on top, garnish with sour cream and sprinkled parsley.
