Balance Moisture in Savory Fillings

Tom identified the central challenge: "getting the flavor without getting too much moisture." Wet fillings like caramelized onions or fresh tomatoes can make dough soggy and prevent proper rising. Reduce liquid fillings by cooking them down completely, and consider thickening with cornstarch or flour. Pat ingredients like fresh mozzarella dry before incorporating, or use aged cheeses that contain less moisture.

The science behind this is crucial - excess moisture creates steam during baking that can cause dough to collapse or become gummy. When caramelizing onions, cook them until they're deeply golden and most liquid has evaporated. For tomato-based fillings, use sun-dried tomatoes or paste rather than fresh. If using fresh herbs, chop them just before assembly to prevent wilting and water release. For cheese-heavy fillings, grate hard cheeses finely so they distribute evenly without creating moisture pockets. Consider pre-baking wet fillings separately and cooling completely before incorporating into dough to ensure they won't release additional moisture during the final bake.