Posted on March 13, 2021 These filled pancakes are served during Russia’s Pancake Week (Maslenitsa) celebration before Lent begins. Traditionally they’re filled with caviar, jam, sour cream, or mushroom filling. These filled pancakes are served during Russia’s Pancake Week (Maslenitsa) celebration before Lent begins. Traditionally they’re filled with caviar, jam, sour cream, or mushroom filling. Advertisement