The question of what has a right to go in the pan can inspire garment-rending passion among paella partisans. Purists will argue there is only one true paella, the classic from Valencia that generally includes rabbit, chicken, two or three types of fresh, local beans, and snails or a sprig of rosemary. (Yes, it’s snails or rosemary: Valencian snails cling to this herb and bring some of its essence to the rice on their own.) But there are many combinations recognized by all but the most extreme traditionalists, from paellas that celebrate the arrival of spring produce, like rabbit and artichoke, to my mother-in-law’s specialty, shellfish. Olive oil and tomatoes are obligatory, as are saffron and sweet Spanish paprika, which give the dish its aroma and color. One thing to leave out: chorizo. It’s just not done. Along with being a slap in the face to tradition, it can overwhelm the other flavors.