Preheat your oven to 200°C/Fan 180°C/Gas 6. Fill and boil your kettle. Scrub the potatoes and chop them into bite-sized pieces. Add the potatoes to a large pan and cover with hot water from the kettle. Add a pinch of salt, pop on a lid and bring to the boil. Turn the heat down a little and simmer for 15 mins, till the potatoes are tender when pierced with a knife or skewer.

Meanwhile, trim the roots and top 3cm off the leek, then halve it and rinse out any grit. Finely slice the leek and scatter it onto a baking tray. Drizzle with 1 tbsp olive oil and season with a pinch of salt and pepper. Toss to coat.

Pop the cod fillets on top of the leek, skin-side down, then spoon the pesto over the cod. Slide the tray into the oven and set the timer for 6 mins.

Trim the dry ends off the cavolo nero, then finely slice the leaves. After 6 mins, take the cod out of the oven. Add the cavolo nero to the tray, around the fish, and drizzle the leaves with 1 tbsp olive oil. Slide back into the oven and bake for 5-6 more mins till the cod is cooked through – it will be opaque and flake easily when pressed with a fork. The leek should be tender and the cavolo nero a little crisp and charred.

While the potatoes and cod cook, peel and grate or crush the garlic. Finely grate the zest from the lemon. When the potatoes are tender, drain them. Put the pan back on a low heat and add the butter. Swirl it round the pan to melt it, then add the garlic and lemon zest. Sizzle for 30 secs, then take off the heat. Tip in the potatoes. Add a squeeze of lemon juice and season with salt and pepper. Roughly crush the potatoes with a fork to mash in the garlicky butter.

Divide the potatoes between 2 warm plates. Add a cod fillet and plenty of roast veg to each plate. Serve with wedges of lemon for squeezing.