Mussels are eaten regularly in Thessalonica, Kavalla, and all over northern Greece. They are sold shucked, in small airtight plastic bags filled with seawater. The packaging and expiration dates--no more than two days later--are stamped on the packet. As in Athens, we rarely find mussels in the fish markets, so each time I travel to the north I always eat a lot of the local specialties: mussels dipped in batter and fried, cooked with rice, or this way in white wine, which I enjoy enormously. At home, I usually cook imported frozen mussels or make this dish with shrimp. If you are not particularly fond of feta cheese, omit it and add more lemon juice. This recipes also makes a good appetizer, served in smaller portions. In a deep, heavy skillet, heat the olive oil and saute the scallions for 2 minutes. Add the mussels or shrimps, and cook for 1 minute. Pour in the wine, and when it starts to boil, add the mustard, chili pepper, half the parsley, and the water or stock. Cook for about 3 minutes, then add the lemon juice, feta cheese, and the rest of the parsley. Do not stir, but shake the pan to distribute the ingredients evenly. Remove from the heat, taste, and add salt if needed (usually feta cheese is quite salty). Let cool to just warm, and serve. It can also be refrigerated for 2 to 3 days. Serve at room temperature. Serves 2-3. From The Foods of Greece by Aglaia Kremezi (Stewart, Tabori & Chang, Inc., copyright 1993 by Aglaia Kremezi). Recipe by: Good Morning America