Slice the Mozzarella into even sticks (about 1.5cm thick and 3cm wide).
Set up three bowls: flour in the first, whisked egg mixture in the second, and breadcrumbs mixed with Italian herbs in the third.
Roll each cheese stick in flour, dip it into the egg, and coat it in breadcrumbs. Repeat the egg and breadcrumb steps for a second coat; this extra layer is crucial to keep the cheese from leaking while frying.
Place the coated sticks on a tray and chill them in the freezer for at least 1 hour to firm up.
While the sticks are chilling, combine the tomato and onion relish, tomato sauce, smoked paprika, sugar, and your choice of vinegar in a small saucepan. Simmer over medium heat for 15-20 minutes, until thick and glossy. Season with salt and pepper, then set aside to cool. If you like a smoother sauce, you can blend it until smooth in a standing blender or with an immersion blender.
Heat about 4cm of oil in a deep pan. Fry the chilled sticks in small batches for 1–2 minutes, until deep golden brown and crispy.
Drain briefly on paper towels and serve immediately while hot and stretchy with a generous side of your smoky tomato dipping sauce.