In a saucepan, bring the broth to a boil; reduce the heat to a simmer and cover. Put the saffron on a 3-inch-wide strip of aluminum foil, fold up the foil to make a square packet, and set the foil directly on the lid of the simmering broth for about 15 minutes. Unfold the packet, transfer the saffron to a mortar (or a small bowl), add a pinch of salt, and use the pestle (or the back of spoon) to crush the saffron. Add about 1/2 cup of the hot broth to the saffron and let the saffron steep for about 15 minutes. Add the saffron-infused liquid back to the broth. Taste; the broth should be well seasoned, so add more salt if necessary. Remove from the heat until ready to add to the rice.
Set a 14-inch paella pan over medium-high heat and add the olive oil. When the oil is hot, add the chicken and the head of garlic; sauté until the chicken is golden, 10 to 15 minutes. The oil may splatter, and you may need to turn down the heat. Transfer the partially cooked chicken to a platter. The head of garlic stays in the pan.
"Start by sautéing the chicken until golden. A head of garlic goes in the pan, too.
Reduce the heat to medium low. In the same pan, sauté the red pepper slices slowly until they're very limp, 20 to 25 minutes, adding more oil if necessary; they shouldn't brown too much. Meanwhile, prepare the artichokes. Cut off the upper two-thirds of the leaves and the stem. Pare away the remaining tough outer leaves. Scrape out the choke fibers and cut the hearts into quarters (or eighths, if large).
Sauté strips of red pepper until completely limp and tender.
When the pepper is done, transfer the pieces to a plate, cover with foil, and set aside. Slowly sauté the artichokes and green beans in the same pan, still on medium low, until the artichokes are golden and tender and the beans are soft and slightly wrinkled, 15 to 25 minutes. Meanwhile, when the pepper pieces are cool enough to handle, peel off and discard the skin. When the artichokes and green beans are done, push them to the perimeter of the pan where there's less heat (or transfer them to the platter with the chicken.)
Sauté the green beans and artichokes together.
If there's more than 1 Tbs. of oil in the pan, pour out the excess. Increase the heat to medium and sauté the grated onion and sliced garlic until the onion is soft (it's all right if it gets slightly brown), about 5 minutes. Add the grated tomato. Season well with salt and sauté until the water from the tomato has cooked out and the mixture, called a sofrito, has darkened to a burgundy color and is a very thick purée, 5 to 10 minutes. If you're not cooking the rice immediately, remove the pan from the heat.
Push the vegetables to the perimeter of the pan to make way for the tomato, onion, and garlic sofrito.
About half an hour before you're ready to eat, bring the broth back to a simmer and set the pan with the sofrito over your largest burner (or over two burners) on medium heat, noticing if the pan sits level. (If not, choose another burner or try to create a level surface.) When the sofrito is hot, add the rice, stirring until it's translucent, 1 to 2 minutes.
Add the rice to the pan, and sauté for a minute or two until translucent.
Spread out the rice (it should just blanket the bottom of the pan), distribute the green beans and artichokes evenly, and arrange the chicken in the pan. Increase the heat to medium high and pour in 3 cups of the simmering broth (reserving 1/2 cup). As the broth comes to a boil, lay the peppers in the pan, starburst-like, and push the head of garlic to the center. Cook until the rice begins to appear above the liquid, 6 to 8 minutes, rotating the pan over one and two burners as necessary to distribute the heat to all areas. Add the sprig of rosemary and reduce the heat to medium low. Continue to simmer, rotating the pan as necessary, until the liquid has been absorbed and the rice is al dente, another 8 to 10 minutes. To check for doneness, taste a grain just below the top layer of rice—there should be a very tiny white dot in the center. If the liquid is absorbed but the rice is not done, add a bit more hot broth or water to the pan and cook a few minutes more. Cover the pan with foil and cook gently for another 2 minutes, which will help to ensure that the top layer of rice is evenly cooked. With the foil still in place, increase the heat to medium high and, turning the pan, cook until the bottom layer of rice starts to caramelize, creating the socarrat, 1 to 2 minutes. You may hear the rice crackling, which is fine, but if it starts burning, remove the pan from the heat immediately. To check for socarrat, peel back the foil and use a spoon to feel for a slight crust on the bottom of the pan.
Ad simmering stock, then arrange the chicken and vegetables in the pan and cook the rice until al dente.
When the rice is done, cover with foil, turn up the heat, and use a spoon to check for a caramelized crust.
Remove the pan from the heat and let the paella rest, still covered, 5 to 10 minutes. Sit everyone down at a round or square table, if possible. Remove the foil, and invite people to eat directly from the pan, starting at the perimeter and working toward the center, squeezing lemon over their section if they like.
Spain's best-known red, Rioja, made from the tempranillo grape, is a great choice for a paella with sausage and red meat. It will also highlight the big, rich flavor, caramelized onion, and browned chicken in the recipe here. Bodegas Montecillo and Conde de Valdemar are reliable producers.
If you make the seafood variation, keep the party mood going with cava, Spain's answer to Champagne; try Castellblanch Brut Zero or Segura Viudas' Aria Brut. For still wine, look to dry whites with crisp, dry, apple-and-apricot-fruity acidity, such as Albariño.
Can't decide between white and red? Strike a happy medium with rosé (rosado in Spanish). Spain makes some of the best. Try Señorio de Sarria (Navaraa), Marqués de Cáceres (Rioja) or Jaume Serra Tempranillo (Penedès).