Cut fish into evenly sized chunks about 2.5cm by 2.5cm or 1 inch square pieces.
In a medium sized saucepan, heat the oil and add the onion, zucchini, garlic, paprika, fennel, salt, and chilli flakes. Cook for 2 minutes on medium to high heat.
Add tin tomatoes, fish stock, tomato paste and water, stirring through. Let it heat through and just before it starts to bubble add in lemon zest and stir.
Reduce head to medium and add cous cous . Stir through for 4 to 5 minutes until cous cous is just cooked.
Add peas and cook for 1 minute
Add fish and cook for a minute or two until fish is cooked through
To Thicken: mix cornflour and water in a small cup/jug until smooth and milky. Stir through the stew gently with a spoon for a minute or two, and it will gradually begin to thicken.
Serve with crusty bread and butter.