Heat the oven to 200C/180C fan/gas 6. Halve any large potatoes so they’re all roughly the same size. Put in a pan of water, bring to the boil and simmer for 8-10 mins until tender. Drain.
Tip the potatoes into a large roasting tray to sit in one snug layer. Drizzle with 1 tbsp oil, season and add the lemon zest, garlic, thyme and bay. Toss to coat the potatoes. Use a potato masher to gently crack each potato, being careful not to break them up too much. Place the chicken on top, rub with the rest of the oil and the paprika, then season. Roast for 45 mins until golden brown and cooked through.
Meanwhile, make the creamed spinach. Boil the kettle and tip the spinach into a colander. Pour over the boiling water to wilt the leaves. Leave to cool.
Heat the butter in a pan. Add the onion and cook for 8-10 mins until softened. Stir through the garlic for another minute, then the flour for another minute. Pour in the milk, a little at a time, stirring and adding more until you have a smooth sauce. Bring to a simmer and stir continuously until the sauce has thickened.
Squeeze any liquid out of the spinach, then roughly chop. Add to the sauce along with the nutmeg. Season to taste. Transfer to a baking dish, top with the cheese, and bake for 15 mins until golden.
Cover the chicken and rest for 5 mins. Set aside 2 legs to cool before chilling for lunch tomorrow. Serve the rest (1 full leg each per adult, a drumstick or thigh each for the children) with the potatoes and spinach alongside some carrots.