Preheat the oven for 200°C. Heat the vegetable oil in a skillet over a medium heat and put a pan of salted water on to heat up for cooking the gnocchi. Add the onion to the oil and fry for a few minutes before adding the garlic.
Put the gnocchi in the water and cook according to package instructions. Once the garlic has been in the pan for 2 minutes add the courgette and cook for 5 minutes until softened. Add the tomatoes, olives and cooked gnocchi along with the oregano and a sprinkling of salt and pepper.
Cook everything for a few minutes then remove from the heat. Top with the mozzarella slices and place in the oven for 10 minutes to allow the mozzarella to melt. Serve topped with chopped basil and a good shaving of parmesan.