Place garlic and salt on a cutting board and smash into a paste with the side of a chef’s knife. Transfer to a small bowl or mortar, add oregano, parsley, pepper and paprika and grind until all is blended. Add oil and mix rub until blended and smooth.
Cover flank steak with rub and refrigerate over night.
Bring steak to room temperature and cut in half lengthwise. Cut a slit in center of each piece meat so that it creates a pocket. Place a layer of mozzarella slices in each pocket.
Prepare a grill over high heat or prepare a broiler. Place steak on grill or under broiler for about 5 minutes, turn and cook for another 4 minutes.
Slice steak into strips and serve immediately.
Plan ahead, this recipe is best when allowed to marinate over night.