Preheat your oven to 200ºC/400ºF/gas 6. Bring a pan of salted water to the boil, add the vermicelli, and cook for slightly less time than it says on the packet. You want it to be al dente. Once ready, drain, rinse in coldwater and leave to cool. Put it into a large bowl and grate in your courgettes. Add the chopped tomatoes, coriander, preserved lemon, cumin, sweet paprika, ground ginger and 1 teaspoon of harissa. Mix it all together really well with your clean hands, then have a taste, add a pinch of salt and pepper if needed, and put aside.
Place the fish on a large chopping board and score the skin every 2cm on both sides at a slight angle, using a sharp knife. Sprinkle over a little salt, a small pinch of cumin, and a pinch each of sweet paprika and ground ginger. Mix the remaining teaspoon of harissa with 1 teaspoon of olive oil and rub half of it into the fish, making sure it gets into the cuts you’ve made. Turn the fish over and repeat on the other side.
Spoon two-thirds of your vermicelli filling into a large baking tray or earthenware-type dish, making a bed for the fish, and gently place the fish on top. Stir your prawns into the rest of the vermicelli filling and spoon this into the cavity of your fish, pushing it right in – don’t worry if it spills out a little. Drizzle over a little olive oil, and roast in the hot oven for around 25 minutes, until the fish is crisp on the outside and cooked through.
To serve, pull the meat off and pick the bones out. Add a spoonful of the vermicelli filling on the side of each plate and serve with a crisp dressed green salad.
PS Any leftover vermicelli will be delicious the next day as a cold salad.