
In a large paella pan or wide skillet, heat olive oil over medium heat. Add the chicken pieces and cook until browned on all sides. Remove the chicken and set aside.
Add the chopped onion, bell pepper, and garlic to the pan. Sauté until the vegetables are softened and fragrant, about 5-7 minutes.
Stir in the crushed tomatoes, smoked paprika, saffron threads, and salt. Cook for another 2-3 minutes, allowing the flavors to meld.
Add the paella rice to the pan and stir to coat it evenly with the tomato mixture. Pour in the chicken broth and bring to a simmer.
Arrange the browned chicken pieces, shrimp, mussels, and chorizo (if using) over the rice. Gently press them into the rice. Do not stir the paella from this point on, as it will prevent the formation of the socarrat.
Reduce the heat to low, cover the pan with a lid or aluminum foil, and simmer for 20-25 minutes, or until the rice is cooked and the liquid is absorbed. The rice at the bottom should be slightly crispy.
Remove from heat and let the paella rest for 5-10 minutes before serving. Garnish with fresh parsley and lemon wedges. Serve hot and enjoy!