Open the mussels, discarding the shells but reserving the liquid. Strain the liquid through a fine sieve or cheesecloth into the eggs. (You may steam the mussels partially to get the shells to open, which is considerably easier than prying them open raw. Don't let them cook any longer than necessary, or they'll be tough and overcooked after frying).
Heat the oil in a deep-frying pan to 370 degrees F. Dip each mussel into the flour, then into the eggs, and then gently lower them into the hot oil and deep-fry until golden.
Drain on paper towels, sprinkle with salt, and serve immediately with salsa.
Combine all the ingredients in a small bowl.