Sauté the hot pepper and the garlic until golden.

Stir in the wine and when it has boiled for a couple of minutes add the mussels. If the mussels are fresh without a shell add a little of the water from the bag that they come in, or else just add some water. Add the mustard as well.

Let everything boil (about 5-7 minutes, they don't need more).

When the mussels are done, add the feta cheese cut into cubes.

Finally, thicken the saganaki by adding  a little flour.