Kids and adults alike will be delighted by this irresistible combination of gooey melted cheese and crisp, golden breading.
Cut mozzarella lengthwise into 1/2-inch-thick slices, then cut again into 4-by-1/2-inch sticks. Place flour in a shallow dish; season with salt and pepper. Whisk eggs with 1 tablespoon water in a separate dish; season with salt and pepper. Stir together breadcrumbs, Parmigiano-Reggiano, and herbs in a third shallow dish; season with salt and pepper.
Dredge mozzarella sticks in flour, tapping off excess. Dip in egg wash, allowing excess to drip off, and coat with breadcrumbs, patting to adhere. Transfer mozzarella sticks to a parchment-lined baking sheet. Freeze until firm, at least 1 hour. (Mozzarella sticks can be covered and frozen at this point up to 2 months.)
Pour enough oil into a heavy pot (preferably cast iron) to come 2 inches up sides. Heat over medium-high until a deep-fry thermometer reads 350 degrees. Working in batches, add mozzarella sticks; cook, turning occasionally, until golden and crisp, 2 to 3 minutes (adjust heat as necessary to maintain oil temperature.) Transfer to a wire rack set over a rimmed baking sheet to drain. Season with salt; serve immediately, with marinara sauce.