Place the breadcrumbs and Parmesan in another shallow dish.
Dunk each mozzarella stick into the flour, shaking off any excess. Then dip into the egg mixture, letting excess drip off. Roll in breadcrumbs to coat. For a thicker crust, repeat the egg and breadcrumb steps.
Transfer the coated mozzarella sticks to a baking sheet and freeze for at least 1 hour.
Heat vegetable oil in a deep frying pan or saucepan to 350°F.
Cook the frozen mozzarella sticks in batches for 1–2 minutes or until golden brown.
Remove the mozzarella sticks with a slotted spoon and drain on paper towels. Serve hot with marinara sauce on the side.