Make the sauce: Heat a large saucepan to medium-high heat and add 3 tbsp olive oil followed by the garlic. Reduce heat and fry for 2 minutes until lightly coloured.
Add the basil stalks, tomato purée, tomatoes, stock, oregano, pinch of salt and pepper. Stir together and place tomato vines on top.
Cover with a lid and gently simmer for 10 minutes. Check seasoning and set aside.
Fry the courgettes: Heat a large frying pan to high heat and pour in the sunflower oil. When hot, carefully add courgette halves spread out in the oil.
Fry for 2-3 minutes, turning once per batch until lightly golden. Lay on paper towel and continue frying in batches for about 15 minutes total.
Preheat the oven to 190°C.
Assemble the parmigiana: Remove vines from sauce. Spoon some sauce into a 9-inch baking tray and spread it out.
Layer courgettes followed by more sauce. Top with ⅓ of the mozzarella, torn basil leaves, ⅓ chickpeas, and grated cheese. Season with salt and pepper.
Repeat to make 2 more layers of filling.
Top with a final layer of courgettes, salt, pepper and 1 tbsp olive oil.
Bake in the middle of the oven for 25 minutes.
Leave to rest for 10 minutes before cutting. Serve hot or at room temperature.
