Preheat the oven to 400 degrees F/200 degrees C/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 (zucchini). Add the chopped tomatoes, coriander (cilantro), preserved lemon, 1 teaspoon harissa, sweet paprika, ground ginger, and cumin. 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 3/4-inch/2 cm 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 1 teaspoon harissa with 1 teaspoon olive oil and rub 1/2 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 2/3 of the vermicelli filling into a large baking tray or earthenware-type dish, making a bed for the fish; gently place the fish on top. Stir your prawns into the rest of the vermicelli filling and spoon this into the cavity of the 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.
NotesAny leftover vermicelli will be delicious the next day as a cold salad.