Cut mozzarella into even sticks if using a block, then freeze until firm, about 20 minutes.
Set up three bowls: flour; beaten eggs; and breadcrumbs mixed with panko, Parmesan, Italian seasoning, garlic powder, salt, and pepper.
Dredge frozen cheese sticks in flour, shaking off excess.
Dip in egg, coat in breadcrumb mixture, then repeat egg and crumbs for a thicker crust.
Place breaded sticks on a tray and freeze 10 minutes while you heat the oil.
Pour oil into a heavy pot to about 2 inches depth and heat to 350°F.
Fry in batches until golden, 60–90 seconds, turning once. Do not overcrowd the pot.
Drain on a rack or paper towels and sprinkle with a pinch of salt. Serve hot with warm marinara.