Remove the mozzarella string cheese from the package and cut each stick into 1" pieces. Place the pieces on a plate.

Set up three coating stations: pour 1 cup milk into a shallow bowl; put 1 cup all-purpose flour into a resealable plastic bag; put 2 cups Panko, 2 teaspoons Italian seasoning, and 1 teaspoon parsley into a second resealable plastic bag and shake to combine.

Working with a few pieces at a time, dip the cheese pieces into the milk to coat them.

Transfer the milk-coated pieces to the flour bag, seal, and shake until evenly coated with flour. Remove the pieces and return them briefly to the plate.

Dip the floured pieces back into the milk so they are fully coated again.

Place the milk-coated pieces into the panko bag, seal, and shake until they are evenly coated with the seasoned Panko. Press the crumbs gently if needed to adhere.

Arrange the coated mozzarella bites in a single layer on a plate or baking sheet (do not let them touch) and freeze for at least 2 hours, until solid.

Heat oil in a deep skillet or pot over medium heat until hot. Fry the frozen mozzarella bites in batches without overcrowding, turning as needed, until they are golden brown on all sides.

Remove the bites from the oil with a slotted spoon or tongs and drain on a wire rack or paper towels. Let them rest briefly to cool slightly.

Serve the mozzarella bites warm with marinara sauce.