Spinach, Chicken, and Mushroom Calzone

My sister made these for us a couple days ago - so yummy!!  I thought it was even better with a little garlic salt or onion salt sprinkled on the crust.

Filling:
½ bag baby leaf spinach
2 cups water
1 ½ cup chopped mushrooms
2 garlic cloves, minced
1 precooked chicken breast, shredded or finely diced
1 T balsamic vinegar
½ tsp salt
¼ tsp pepper
Dash of crushed red pepper
½ cup grated mozzarella cheese
¼ cup grated cheddar cheese
¼ cup grated parmesan cheese

Crust:
1 cup boiling water
1/3 cup yellow cornmeal
2 cups flour
½ tsp salt
½ tsp thyme
1 T honey
1 ½ tsp olive oil
¼ warm water
2 ¼ tsp dry yeast

Glaze:
1 ½ tsp water
1 egg white

CRUST: Boil water and stir in cornmeal. Let sit for about 15 minutes, stirring occasionally. Mix wet and dry ingredients in separate bowls. Combine all together with cornmeal mixture. Knead for a few minutes and let rise for about 3 hours.
FILLING: Boil water; add spinach and cook for one minute. Plunge spinach in ice water and let drain. Squeeze out remaining water. Heat pan coated in cooking spray over med-high head. Add mushrooms and garlic and sauté for 5 minutes. Add chicken, spinach, salt, vinegar, black and red pepper. Cook for 1 minute.
Preheat oven to 450 degrees. Divide dough into 4 balls. Roll out each ball to make an approximately 70inch circle. Place ½ cup filling in ½ of each circle, leaving a 1 inch border. Sprinkle with 2 T mozzarella, 1 T cheddar and 1 T parmesan cheese. Fold dough over until edges almost meet. Pull bottom dough up over the dough on top. Crimp edges with finger. Place calzones on a pizza pan coated with cooking spray or a pizza stone sprinkled with cornmeal. Brush each one with glaze and bake for 12 minutes Serve with marina sauce for dipping.