Babka is traditionally filled with either walnut, chocolate, poppy seeds or a mix of cinnamon and sugar. But what makes babka truly special is the way the loaves are shaped: The dough is rolled up around the filling and then sliced down the length to create two long pieces streaked with filling. Twist those pieces around each other, pop them in a loaf pan, and you have babka in all its twisty, layered glory.