Heat ground nut oil in a tagine and cook onion and garlic until soft.
Add cumin, ginger, cinnamon, lemon, and olives and cook for two minutes.
Blend chillies, garlic, lemon juice, and olive oil in a food processor to make harrissa.
Stir one tablespoon of the harrissa into the tagine and cook for one minute.
Add white wine, 200ml fish stock, and saffron then bring to a simmer.
Add 500g mixed fish, 200g mussels, and 100g cherry tomatoes to the tagine.
Season with salt and pepper, cover, and cook gently for 6-7 minutes.
Serve over steamed couscous and garnish with fresh coriander.