How to Make It
In a medium saucepan, combine the chicken stock with the fish stock and crumbled saffron and bring to a simmer.
Meanwhile, in a 15-inch paella pan or large enameled cast-iron casserole, heat the olive oil. Add the onion and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Add the garlic and paprika and cook until fragrant, about 2 minutes. Add the rice and cook, stirring, until it is evenly coated in the oil, 1 minute. Add the hot broth and stir the rice once to evenly spread it in the pan. Cook over moderate heat, without stirring but rotating the pan for even cooking, until half of the liquid is absorbed, about 15 minutes. Reduce the heat to low. Nestle the chorizo and shrimp into the rice. Add the clams, cockles and mussels hinge side down and cook, turning the shrimp halfway through, until the shrimp and shellfish are cooked through and all of the liquid is absorbed, about 20 minutes. Scatter the peas on top and let stand for 5 minutes. Garnish with parsley and serve.