Put the spinach in a colander over the sink and slowly pour over a kettle full of boiling water. Leave to drain and cool before squeezing out the excess water. Roughly chop and transfer to a bowl.
Heat the oil in a small frying pan, add the onion, garlic, fennel seeds and crushed chillies and cook for 5 minutes until softened. Add to the spinach along with mince, breadcrumbs and parsley, reserving a small amount of parsley to garnish. Mix well to combine.
Preheat the oven 190°C, fan 170°C, gas 5. Pour about two thirds of the passata into the bottom of a 20x30cm ovenproof dish and sprinkle over half of the dried herbs. Fill the cannelloni tubes with the mince mixture and place on top of the passatta. Pour over the remaining passata, scatter over the herbs and top with the mozzarella. Bake for 40 minutes until golden.
Serve garnished with the reserved parsley and the salad on the side.