Mix skim milk, egg, 1 soup spoon of oil, salt and pepper in a baking bowl with a whisk. Add the flour until a thick dough is formed. Cover the dough with a cloth and let it rest for an hour.
Brush the mussels thoroughly under running tap water. Discard any that have already been opened. Saute the mussels with a tiny bit of tap water in a large saucepan over high heat for 5-7 minutes with the lid closed.
Once all glass shells are opened, drain mussels in a colander and let cool. Discard any mussels that are not open. Using a fork, loosen clam meat from glass shells and drain.
Heat the remaining olive oil vigorously in a frying pan. Dip the mussels one by one into the batter and fry in the oil over medium heat until golden. Then drain them on a kitchen towel and place them on the table while still hot.
Tip: Use better olives – it pays off!