Preheat oven to 400 degrees.
Wash squash and cut in half lengthwise.
Using a spoon, scoop out seeds.
Place halves cut side down in 13x9 baking pan.
Add a small amount of water, and cover pan with foil.
Bake for 30-45 minutes or until fork tender.
Allow squash to cool for 15 minutes. (Leave oven on.)
Using a fork, remove squash from shell.
Measure 3-1/2 cups squash, and transfer to a mixing bowl. (Save remaining squash for another dish.)
Allow squash to cool for another 15 minutes.
Add garlic, egg, parmesan, and 1/4 cup mozzarella; mix well.
Spray a muffin pan with nonstick cooking spray.
Divide mixture evenly among muffin cups.
Bake for 15 minutes.
Remove pan from oven, and top squash muffins with remaining 1/2 cup mozzarella.
Bake for 5 more minutes.
Serve hot with marinara, if desired.