Microwave whole dried chilis for approximately 15 seconds until pliable. If needed, microwave 15 additional seconds. Cut the tops of the dried chilis, and create a split down the side using kitchen shears. Remove seeds and any large ribs. Cut into 1/2 inch pieces. Place in a microwave safe bowl with 1 cup vegetable stock. Microwave for 4-5 minutes, checking halfway through for "tenderness".
Using a food processor, blend together the peppers and 1-2 Tablespoons of the stock it cooked in (keep the rest! you'll use it later). Puree until a paste forms. Add the tomatoes, with some of the liquid drained. Puree until mixed. You may want to strain out the sauce if there are still tough skins, but I generally just leave it.
In a large stock pot or dutch oven, heat butter over medium-high heat. Add finely chopped ginger and garlic, salt, and saffron. Cook for 1 minute, stirring continuously. Add white wine. Add tomato and chili mixture, stirring to combine. Add the remaining vegetable stock in which the peppers cooked in. Simmer for 3-4 minutes; taste for salt and pepper levels, adjusting as needed. Add the additional 1/2 cup of vegetable stock to thin out the sauce - add more depending on personal preference for mussel broth (it will be a little on the thicker side).
Add the cleaned mussels to the pot, cover, and cook for approximately 5 minutes, if some mussels are still closed at this point, cook for an additional 1-2 minutes. At this time, discard any unopened mussels.
Top with cilantro and serve with bread to sop up the broth. Finish with a lime or lemon squeeze if desired.
Notes
Check out this article to learn how to clean and debeard mussels!