Use fresh shredded cheddar cheese for better melting and texture compared to pre-shredded., Thoroughly drain frozen spinach to avoid excess moisture and soggy casserole., Allow cream cheese to soften at room temperature for smoother blending., Cool turkey mixture before adding egg to prevent scrambling., For doubling the recipe, use a 9×13-inch dish and bake for 30–35 minutes, watching for bubbly edges., Freeze cooked casserole wrapped tightly for up to 3 months; reheat by thawing overnight and baking at 350°F for 25 minutes., Alternatively, freeze assembled casserole before baking; bake from frozen at 375°F for 50–60 minutes, loosely covered with foil., Reheat individual portions covered in microwave for 1–2 minutes or in oven at 325°F for 10–15 minutes., Optional add-ins: red pepper flakes or hot sauce for spice; sautéed mushrooms, zucchini, or bell peppers; alternative cheeses like mozzarella or pepper jack; dairy-free cream cheese and plant-based cheese for dairy-free versions; crunchy toppings like almond flour crackers, breadcrumbs, or crispy onions., Adjust seasoning carefully as cheese adds salt., Make mini portions without spinach for picky eaters.