Achieving that beautiful swirl in your Nutella babka takes a bit of practice, but it's not as challenging as it may seem. To ensure a well-defined swirl, make sure the dough is rolled out evenly and thinly. When spreading the Nutella (or your chosen filling), leave a small border around the edges to prevent it from seeping out. Gently and evenly roll the dough into a log, starting from one of the long edges. Finally, when twisting the log, be sure to keep the layers intact and handle it gently to maintain its shape.