Heat oil in a large, heavy stockpot over medium heat. Add shallot; cook, stirring occasionally, until soft, about 3 minutes. Add garlic and red-pepper flakes; cook, stirring occasionally, 3 minutes. Add wine; bring to a boil. Add tomatoes and chorizo. Reduce heat, and simmer, stirring occasionally, 15 minutes. Season with salt and pepper.
Add mussels. Cover, and continue to cook, shaking pot occasionally.
We thought this was an excellent recipe and we eat a lot of mussels, prepared many ways. We didn't find dried chorizo readily available, so we used the fresh, about 4 oz.. Decrease the amount of oil added to the pan and cook the chorizo along with the garlic/shallots, then added the tomatoes, wine. All the luscious flavors stick to the mussels and make an amazing sauce to dip into with toasted baguette.