Preheat the oven to 220°C/Fan 200°C/ Gas 6. Arrange the chicken, potatoes and chorizo in a 30 x 20 x 5 cm baking tray, pour over the olive oil and season really well. Toss to coat, then put the chicken skin-side up and cook in the oven for 25 minutes, or until the chicken is turning golden and the chorizo has released some of its lovely red oils.
Meanwhile, in a bowl, mix the wine, stock cube, boiling water and leek together and season very well. Remove the tray from the oven and carefully spoon out about 2 tablespoons of the red chorizo oil into a small bowl and set aside. Pour the wine mixture into the tray and stir, making sure the chicken is on top.
Return to the oven for 30 minutes, or until the chicken is cooked through and the potatoes are very tender. For the smoky aioli, mix the reserved chorizo oil, the smoked paprika, crushed garlic and mayonnaise with some seasoning together in a small bowl. Set aside.
Put the chicken onto serving plates and toss the spinach through the potatoes, allowing the heat of the tray to wilt the spinach. Scatter over the lemon zest and taste for seasoning. Serve immediately with the chicken and a dollop of smoky aioli.