Combine the brine ingredients and leave the chicken brining for 6 hours. Drain and pat dry when ready.
For the chimichurri sauce, bash all the ingredients together in a pestle and mortar. Set aside, seasoning with a little salt and a good grinding of black pepper, adding a little olive oil to bring together.
Cook the potatoes in a large pan of boiling water for 15 minutes until tender. Meanwhile, in a large frying pan, heat the oil and cook the onion and chorizo together for 10 minutes. Drain the potatoes and add to the pan with the chorizo and cook for a further 10 minutes.
Place the chicken on clingfilm over a chopping board and slice through each fillet horizontally, making sure not to cut all the way through, then open out. Add another layer of clingfilm and bash lightly with a rolling pin to flatten further. Scatter over the garlic, paprika, lemon zest then rub in with a little olive oil and salt & pepper.
Grill, barbecue or fry your chicken until thoroughly cooked through. Back at your potatoes, add the tomatoes, chilli and paprika and cook for a further 5 minutes. Squeeze over lemon juice and scatter over parsley.