Peel and finely chop the onion. Trim the dry ends off the celery, then finely chop it to match the onion. Put a deep frying pan or wok on a medium heat and add 1 tbsp olive oil. Add the chopped veg and a pinch of salt and pepper. Fry, stirring, for 5-6 mins, till the veg start to look glossy.

While the veg fry, fill your kettle and boil it. Tip the couscous into a heatproof bowl and pour in 300ml boiling water from the kettle. Stir to mix, then cover the bowl with a plate and set aside for 10 mins to soak. The couscous will absorb the water and become tender.

Peel and crush or grate the garlic. Finely chop the parsley stalks (keep the leaves for later). Stir the garlic and parsley stalks into the veg. Cook, stirring, for 1 min.

Pour the cherry tomato passata into the pan and add 100ml boiling water. Stir to mix, pop a lid on the pan (or use a baking tray if you don't have a lid) and simmer for 5 mins to thicken the sauce a little. Taste and add a pinch of salt or pepper if you think it needs it.

Carefully add the whiting fillets to the tomato sauce, skin-side down. Put the lid back on and simmer for 4-5 mins till the whiting is cooked – it will be white, opaque and will flake easily when pressed with a fork.

Fluff the couscous with a fork and divide between 2 warm plates or bowls. Spoon the sauce and fish over the top. Scatter over the flat leaf parsley leaves and serve.