Our adaptation of a pretty and sophisticated appetizer from Kaatje bij de Sluis in Blokzijl, the Netherlands.
8 ounces (about) thinly sliced smoked salmon
1/4 cup olive oil
Boil vinegar and shallots in heavy medium saucepan until almost no liquid remains, about 6 minutes. Add clam juice and oil; simmer until reduced to 1 cup, about 10 minutes. Whisk yolks in medium bowl. Gradually whisk in simmering sauce. Return sauce to pan; stir over medium-low heat until thermometer has registered 140°F for 3 minutes (do not boil). Strain into bowl. Mix in dill. (Can be made 8 hours ahead. Chill.)
Preheat oven to 425°F. Line cooking rack with waxed paper. Butter 2 baking sheets. Place 1 phyllo sheet on work surface. Brush with melted butter. Top with second sheet. Brush with butter. Continue layering and buttering with remaining sheets. Cut phyllo into twelve 4 1/2×2-inch rectangles. Place on prepared sheets, spacing apart. Sprinkle with sesame seeds. Bake until phyllo is golden, watching closely to prevent burning, about 8 minutes. Using metal spatula, transfer phyllo to waxed paper-lined rack; cool.
Rewarm sauce over low heat, stirring constantly (do not boil). Place 4 phyllo rectangles on work surface. Cover each with salmon. Season with pepper. Sprinkle each with 1/2 teaspoon onion. Spoon 1 teaspoon sauce over. Top each with another phyllo rectangle, then salmon. Season with pepper. Sprinkle each with 1/2 teaspoon onion. Spoon 1 teaspoon sauce over. Top with remaining phyllo rectangles.
Whisk oil and vinegar in large bowl. Add curly endive and toss to coat. Season with salt and pepper. Divide salad among 4 plates. Top each with 1 napoleon. Serve, passing remaining sauce separately.