Heat some oil in a large paella pan or skillet over medium-high heat until shimmering. Add the chorizo and cook, stirring, until browned, then remove and reserve. Pat the chicken dry with paper towels and sprinkle on both sides with salt and pepper. Gently place the chicken in the pan skin-side down and cook until browned, about 4 minutes. Flip the chicken and cook on the second side until browned, about 4 minutes more. Remove the chicken to a plate. Add the bell pepper, onion and garlic and cook, stirring, until soft, 4 to 5 minutes.
Meanwhile, soak the saffron in 3 tablespoons water in a small bowl. Add the rice to the pan and cook, stirring to coat the rice with oil, until the rice is toasted, about 3 minutes. Add the saffron and its soaking water and stir to combine. Add 5 cups of the stock, any reserved juices from the chicken and the tomatoes and bring the liquid to a simmer. Return the chicken to the pan, nestling it into the rice, and cook, uncovered, moving the pan around every few minutes and adjusting the heat as necessary to maintain a gentle simmer, until the rice is quite al dente and has absorbed all the liquid, 12 to 15 minutes. (If the pan gets dry before the rice is ready, add some of the remaining stock.)
Nestle the clams into the rice hinge-side down and cook, without stirring, for 5 minutes. Add the mussels hinge-side down along with the shrimp and chorizo. Top with the peas and cook without stirring until the clams and mussels open and the shrimp turns bright pink, 5 minutes more. When the paella is cooked and the rice looks fluffy and moist, turn the heat up for 40 seconds until you can smell the rice toasting at the bottom?it will form a dark brown, crispy crust on the bottom called soccarat. Discard any shellfish that does not open. Remove from the heat and serve immediately, family-style.
This recipe has been updated and may differ from what was originally published or broadcast.