For a richer flavor, use brown butter in the panko topping. Simply melt the butter in a saucepan over medium heat and cook until it turns a nutty brown color. Let it cool slightly before mixing with the panko. Feel free to experiment with other herbs, such as sage or rosemary, in the panko topping. A sprinkle of grated Parmesan cheese over the panko topping before baking adds a savory touch. Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave before serving.