In Bilbao, these stuffed mussels are called Tigres because of their fieriness. I fondly remember the crowded little bars in the old part of Bilbao, where orders of tigres would emerge by the dozens from the tiny kitchens. We devoured these mussels and everyone dropped the empty shells right onto the floor, where periodically they would be raked up. This tapa is not as popular today in the bars as it once was, but I like it so much that I make it whenever I find fresh mussels.
Steam open the mussels. Put them in a deep pan with the water. Cover the pan and put over a high heat, shaking the pan, until the shells open. Remove from heat and discard any mussels that do not open.
Mussels can also be opened in a microwave. Place them in a microwave-safe bowl, partially covered, and microwave at full power for one minute. Stir and microwave one minute more. Remove any mussels that have opened and microwave one minute more. Again remove open ones. Repeat twice more. Discard any mussels that have not opened.
When mussels are cool enough to handle, remove and discard the empty half shells. Loosen the mussel meat from the bottom shell and arrange the mussels in their shells on a tray in a single layer. Strain the mussel liquid and reserve it.
Heat the two tablespoons of oil in a saucepan and sauté the minced onion until it is softened, without letting it brown. Stir in the flour, cook for a minute, stirring, then whisk in the wine and the mussel liquid. Cook, stirring, until the mixture is thickened and smooth. Put a spoonful of this white sauce onto each mussel and smooth it level with the top of the shell.
Refrigerate until the sauce is firmly set, at least one hour. Place the beaten egg in one dish and the bread crumbs in another. Dip the mussels, open face down, first into egg, then bread crumbs. Arrange them on the tray in a single layer. (The mussels can be prepared up to this point, then frozen. Freeze them in one layer, then pack them carefully in a freezer bag or plastic container. Let them thaw at least one hour before continuing with the preparation.)
To fry the mussels, heat enough oil to cover the bottom of a frying pan. Fry them in two or three batches, breaded side down, until golden brown. Drain briefly on paper towels and serve hot.
Basque Recipes: Basques live for cooking and eating. I haven't found a similar level of passion anywhere I have traveled. If we try to describe Basque cuisine, a fair answer might be that it is deeply felt, honors tradition, and respects the natural flavors of the ingredients. These qualities are on display in the significant number of dishes that are distinctively Basque.
Tapas are Spain's greatest food invention. "Eat when you drink, drink when you eat" is the philosophy. Spanish men traditionally drink outside the home and rarely alone. They are not meant to be a meal (although a ración is a substantial portion). One tapa per person and a different one with each drink is the idea, then everyone enjoys tasting and sharing.