Preheat oven to 350°F. Spray a baking sheet with cooking spray or fit with a baking mat. Set aside.
In a large mixing bowl, combine the turkey, spinach, onion, garlic, three eggs, breadcrumbs, Parmesan, cream cheese, red pepper flakes, fennel, and oregano until well-combined. Set aside.
Divide the pizza dough into eight equal balls. Take one ball, and roll out on a non-stick surface until about 10" wide.
Place one heaping cup of the turkey filling in the middle of the dough, and then sprinkle with ¼ cup of the mozzarella cheese.
In a small bowl, whisk together the remaining egg and water. Using a pastry brush, brush the edge of the dough, and then fold in half, and seal the edge (I used a fork to press the two pieces together, and then rolled them in to really seal it). Drag a sharp knife across the top of the calzone in a few places to add texture, if desired.
Transfer the calzone to the prepared baking sheet, and then brush top with egg wash. Repeat process with remaining dough and filling.
To bake immediately: bake in preheated oven for 35-40 minutes, or until the crust is golden brown, and the inside registers 170° on a meat thermometer. Let cool for 10 minutes, then serve with marinara sauce for dipping.
To freeze: place the calzones on a baking sheet, and place in the freezer for an hour or two, until frozen. Then transfer to a labeled zip-top freezer bag.
To reheat: remove the calzones from the freezer in the morning, and then bake as usual once defrosted.
Notes
You can also turn these into mini calzones for a fun and festive appetizer or snack. Just split the dough into smaller balls and use less filling. These will last in the freezer just fine for six months. To get even longer, wrap each calzone (after they are flash frozen) in a layer of plastic wrap before putting into the freezer bag.Adapted from Rachel Ray