In a large pan (preferably a paella pan), heat the olive oil over medium heat. Add the chorizo and sauté until browned, about 4 minutes. Remove the chorizo with a slotted spoon to a plate and set aside.
Add the shrimp to the pan and sauté just until they begin to turn pink, about 1 minute. Remove with a slotted spoon and place on another plate. Repeat with the squid, cooking for about 1 minute, and transfer that to the plate with the shrimp. Add the onion, pepper, and garlic, season with salt and pepper and sauté over medium heat until the onion and pepper begin to turn tender, about 3 minutes.
Stir in the rice, paprika, and the saffron, and cook, stirring constantly, until the grains are well-coated with the oil and vegetable mixture. Stir the chorizo back into the mixture. Pour the wine into the pan, then add the broth and tomatoes, and bring to a simmer over medium high heat. Reduce the heat to medium low, cover the pan, and continue to simmer gently until the rice is tender and has absorbed most of the liquid, about 20 minutes.
Turn the heat up to medium, remove the lid and gently stir in the partially cooked shrimp. Add the mussels or clams and cover with the lid. Let the paella cook for another 8 minutes or so, until the shrimp and the rice are just about cooked and the mussels or clams have opened. Lift the lid and distribute the partly cooked squid on top, then sprinkle the top of the paella with the peas. Cover the pan, and let the paella cook for another 3 to 4 minutes until the seafood has cooked through and the peas are cooked and bright green. Garnish with lemon wedges and sprinkle the paella with the parsley. Serve hot from the pan.