If using a block of mozzarella, cut into 12 sticks about 3/4" x 3/4" x 3.5". If using preformed string cheese, leave whole. Line a tray with parchment and place the sticks in a single layer. Freeze for at least 45 minutes (preferably 1 hour) to ensure they hold their shape during frying.

Make coatings

Set up a three-station coating area: Bowl 1 — mix the flour and cornstarch with 1/2 tsp kosher salt and 1/4 tsp black pepper. Bowl 2 — whisk eggs with 2 tablespoons milk until smooth. Bowl 3 — combine breadcrumbs, grated Parmesan, dried oregano, garlic powder, remaining 1/2 tsp kosher salt and 1/4 tsp black pepper.

Dredge each frozen cheese stick first in the flour/cornstarch mixture, shaking off excess, then dip into the egg wash, and finally press into the breadcrumb mixture to coat completely. For a sturdier coating, place coated sticks on a tray and freeze for another 15–20 minutes, then repeat the egg and breadcrumb step to create a double coating. Return to freezer for 15 minutes before frying.

Frying

Pour oil into a medium, heavy-bottomed pot to a depth of about 2" (approximately 1–2 cups depending on pot size). Heat oil over medium-high until it reaches 350°F (175°C). If you don't have a thermometer, test with a small breadcrumb; it should sizzle and brown in about 30–45 seconds.

Fry the cheese sticks in small batches (3–4 at a time) for 45–60 seconds, turning once, until golden brown. Do not overcook: remove as soon as golden. Use a slotted spoon to transfer to a wire rack or paper-towel–lined tray to drain. Allow oil to return to temperature between batches.

If coating was frozen, frying time may be slightly longer (up to 75 seconds) but avoid over-browning. Let the sticks rest 1–2 minutes before serving so cheese is slightly set and not burning-hot inside.

Optional sauce

Warm the marinara in a small saucepan over low heat until gently simmering, stir in crushed red pepper flakes to taste, and serve alongside the cheese sticks for dipping.