Step 1Place the mussels in a large pot with 1/4 cup of water and cover. Steam the mussels over high heat until they open, about 4 to 5 minutes. Discard any empty half-shells. Strain the liquid and reserve it.
Step 2Cook 4 to 6 unpeeled shrimp in boiling water 1 minute. Reserve them and add the cooking liquid to the mussel liquid. Shell the remaining shrimp and set them aside. (If preparing a broth in which to cook the rice, the shrimp shells can be cooked with the stock.)
Step 3Heat the oil in a 12-inch paella pan. Cook the pieces of chicken and pork on medium heat until they are lightly browned, 4 to 5 minutes. Add the pieces of squid and continue cooking.
Step 4Add the bell pepper and garlic and cook 2 minutes more. Add the tomato and increase the heat so it quickly loses its liquid. Stir in the peeled shrimp, peas or fava beans and artichokes, if using.
Step 5Add enough water or broth to the reserved liquid to equal 4 cups. Add the liquid to the pan and bring it to a boil over high heat. Add the rice.
Step 6Combine the saffron, pimenton and food coloring with 1/4 cup of water. Dribble this into the pan. Add pepper to taste, the bay leaf and salt (if the broth was salted, less will be needed). Stir to distribute all the ingredients. Cook on high heat for 5 minutes.
Step 7Reduce the heat and cook 10 minutes more. Do not stir the paella. Arrange the mussels and cooked shrimp on top of the rice. Garnish with strips of pimento. Add additional liquid if necessary.
Step 8Cook until the rice is tender and all the liquid is absorbed, 5 to 6 minutes more.
Step 9Let the paella rest 5 to 10 minutes before serving. Place a half-lemon in the center or lemon wedges around the edges. Many people like to add a squeeze of lemon to their serving of paella.