Boil eggs until hard. Place in cold water to cool. Peel and cut in half. Chop finely and set aside.
Clean mussels of any debris on outer shells and rinse thoroughly. Pour approximately 1 to 1 1/2 cups cold water and a pinch of salt into a medium saucepan and bring to a boil. Add mussels and cover. Steam until shells open (approximately 3 to 5 minutes). Discard any mussels that do not open their shells. Pour broth into a bowl and reserve for use later. Allow mussels to cool for 10 minutes, or until shells are cool enough to touch.
Remove mussel meat from shells. Keep the shells to fill. Finely chop the mussel meat.
Finely chop leek (white portion only), onion and green pepper. Place a medium frying pan over low heat and sauté the vegetables in a few tablespoons of olive oil until they are transparent and soft. Add the chopped mussels and a few teaspoons of white wine. Stir, continuing to sauté 1-2 minutes. Add chopped boiled egg, 2 tablespoons of tomato sauce and salt to taste. Mix thoroughly. Remove from heat and allow to cool 5 to 10 minutes.
Once filling has cooled, fill mussel shells with mixture. Spoon approximately 1 1/2 tablespoons of mixture into each shell, filling it completely.
Pour 4 tablespoons olive oil into a small sauce pan and heat on medium. When hot, add approximately 3 heaping tablespoons flour into pan and stir, frying the flour. Continue to stir with a fork or wire whip, so that sauce does not form clumps. While stirring constantly, add reserved broth. When broth has been absorbed, the sauce should be thickening. Slowly pour in milk while stirring. Add pepper and mix thoroughly. For this recipe, the béchamel sauce should not be too thick.
Before béchamel sauce cools, spoon over filled mussel shells, covering mixture completely. (Don’t worry if sauce drips off the shells a bit.) Set on a platter or large plate and sprinkle each filled shell with bread crumbs before béchamel cools. (Once cooled, a thin film will form on top and bread crumbs will not stick.) Allow tigres to cool completely, then refrigerate or freeze if they will not be fried immediately.
Beat two eggs in a wide shallow bowl or small baking dish. Pour breadcrumbs into a small bowl. Set both bowls close to stove. Pour olive oil into a large heavy-bottomed frying pan to a depth of 1-inch (approximately 16 to 20 ounces). Heat on medium. While waiting for oil to heat, quickly dip filled side of the shells into the beaten egg, then roll in the bread crumbs. Fry in pan, until upper crust is golden. Remove and allow to drain on a paper towel. Serve warm.
Optional: Sprinkle a bit of oloroso sherry on top of each tigre for added flavor just before serving.