Put the flour, egg and breadcrumbs into three separate bowls, seasoning each. Stir the dried oregano and garlic granules into the breadcrumbs.
Coat the mozzarella sticks in the flour, dust off any excess, then dip into the beaten egg. Gently shake to remove the excess egg, then turn in the breadcrumbs until well-coated. Transfer to a baking sheet lined with baking parchment and arrange in a single layer, then freeze for 1 hr until completely solid.
To make the dipping sauce, heat the oil in a saucepan, and fry the chillies and garlic for 2-3 mins until fragrant. Tip in the tomatoes, vinegar, sugar and some seasoning. Reduce the heat to a simmer and cook for 12-15 mins until thick and saucy. If you prefer a smooth sauce, blitz with a stick blender. Season to taste – you may need to add a little more sugar, vinegar or salt. Leave to cool. Will keep, covered in the fridge, for up to three days, or the freezer for up to three months.
Fill a heavy-based saucepan no more than a third full of oil and heat to 180C, or until a cube of bread sizzles when dropped into the oil, and browns in about 30 seconds. Gently lower in the frozen mozzarella sticks – you’ll need to do this in two batches to ensure the temperature remains high – and fry for 2-3 mins until the cheesy middle is melted and the outside is crisp and golden. Drain on kitchen paper. Serve straightaway, or leave to cool. Will keep, covered in the fridge, for up to three days, or the freezer for up to three months.
To reheat, heat the oven to 220C/200C fan/gas 7 and bake on a tray for 8-10 mins until heated through. Season and serve with warm dipping sauce.