• Season the chicken with salt and pepper and let stand 30 minutes at room temperature.
• Place the chicken in a large pot and add the stock and enough water to cover it. Add the onion, garlic, bay leaf, celery, and bring to a boil. Skim foam off the top if any (if it appears later, skim again), cover the pot, and simmer for 10 minutes over low heat. Add the carrots and potatoes and simmer for 15 minutes more.
• Meanwhile, in a pot of boiling water, cook the chorizo sausages for a couple of minutes and drain them. Add the sausages and chickpeas to the pot with the chicken. Cover and continue simmering until the chicken is cooked through. It should take about 20 minutes.

The sauce:

• In a food processor, add the parsley, tomatoes, and 1/3 cup of the chicken cooking liquid. Process until the tomatoes are crushed but not pureed.
• Transfer the mixture to a bowl. Add the onion, garlic, vinegar, olive oil, and whisk well. Season with salt and pepper to taste.
• For the traditional style of serving: Transfer the chicken and chorizo to a cutting board. Carve the chicken (if using a whole), slice the chorizo, and arrange on a serving platter. Pour some cooking liquid over. Now transfer all the veggies and chickpeas (using a slotted spoon) to another plate. Discard the onion, celery, garlic, and bay leaf. Once again pour some cooking broth over. Serve accompanied by the sauce.
• Alternatively, you can simply serve the meats, veggies, and chickpeas in one bowl drowned in the cooking liquid. Enjoy!