To make ahead: Prepare through Step 4 up to 1 day in advance. Cover and refrigerate the broth, tomatoes and mussels in separate containers.
Tip: To clean & debeard mussels: Use a stiff brush to scrub mussels under running water. Discard any with broken shells or any whose shells remain open after you tap them lightly. Scrape off any barnacles; pull off the black fibrous “beard”.
Note: Literally the dried stigma from Crocus sativus, saffron is the world's most expensive spice. Over 75,000 flowers are required for each pound of saffron. Fortunately, a little goes a long way. It's used sparingly to add golden yellow color and flavor to a wide variety of Middle Eastern, African and European-inspired foods. Find it in the specialty-herb section of large supermarkets, gourmet-food shops and tienda.com. Wrapped in foil and placed in a container with a tight-fitting lid, it will keep in a cool, dry place for several years.
2 1/2 lean protein, 2 1/2 vegetable, 1 fat