Add the saffron to the hot chicken stock and leave it to infuse while you start the paella. This little step makes a huge difference to the colour and flavour.
Heat 2 tablespoons of the oil in a paella pan or wide frying pan over a medium-high heat. Fry the chicken for 6-8 minutes until lightly golden but not cooked through, then remove it with a slotted spoon.
Add the remaining oil to the pan and reduce the heat to medium. Next, add the onion, chilli, and pepper, and cook for 6-8 minutes until softened.
Stir in the garlic and chorizo and cook for a few minutes until the chorizo releases its red, smoky oil. Then add the paprika and stir well to coat everything in the spices.
Return the chicken to the pan, add the tomatoes, and cook for another minute. After that, pour in the wine and let it bubble away for a minute so the alcohol cooks off.
Stir in the rice and cook for a couple of minutes until each grain is coated in the oil and wine. Then add the saffron stock, season with salt and pepper, and bring everything to a gentle boil.
Reduce the heat, cover with foil or a tight-fitting lid, and simmer gently for 16-18 minutes. Check once during the first 5-10 minutes, and if the pan starts looking dry, add a small splash of water, but do not stir again.
Add the peas, lemon zest, and prawns, if using, then cover again and cook for 3-4 minutes without stirring. If you want a crispy base, turn the heat up very high for 30-60 seconds at the end, but watch carefully so it does not burn.
Turn off the heat and leave the paella to rest, covered, for 5 minutes. Finally, remove the lid, check the seasoning, and garnish with chopped parsley and lemon wedges before serving.