This recipe for polish meatballs in sour cream with mushrooms is known as klopsiki w mietanie grzybami (klohp-see-kee vef shmeh-tahn-yeh zhih-bah-mee). They can be made with any combination of ground pork, beef, and veal. The meatballs stay tender if they're browned in a skillet on the stovetop and then transferred to the oven to finish cooking. They can be served with a pan gravy or mushroom sauce and a side of mashed potatoes, dumplings, or rice.