In a shallow bowl, whisk together the flour, seasoned breadcrumbs, salt, and ground black pepper. Set aside.
In another bowl, whisk together the egg and the milk. Set aside.
Place a wire cooling rack onto a baking sheet.
Working with one piece of the string cheese at a time, fully dip the cheese in the egg mixture and coat well with the breadcrumb mixture. Place the coated cheese string onto the wire cooling rack to set.
Continue to do this until all of the cheese strings are coated.
Again, working with one coated string cheese at a time, fully submerge it into the egg and then roll into the breadcrumbs. Place it back on the wire cooling rack and continue until all strings have been coated a second time.
Repeat this action so that each cheese string is coated a total of 3 times. Set aside.
Add enough vegetable oil to a wide pot so that there is 3-4 inches of oil in the pot. Heat the oil to 350 degrees. If you don’t have a thermometer, you can test the temperature of the oil by dropping in a pinch of the leftover breadcrumb mixture. If it sizzles and floats to the top, the oil is ready.
Fry the mozzarella sticks in batches. Lower them into the oil and allow them to fry until golden brown. Turn them over and fry them for another minute or two. Remove from the oil and place onto a wire cooling rack with a sheet pan underneath to catch any oil that drops.
Garnish and serve hot with your favourite dipping sauce.