To make the dressing: In a small bowl, whisk together the vinegar, mustard, truffle paste, olive oil, and salt and pepper to taste. Set aside.
To make the crostini: Preheat the broiler.
Brush the cut sides of the baguette slices with olive oil, and place under the broiler just until the bread is toasted on both sides. Set aside.
In a medium saucepan, heat 1 tablespoon of the olive oil and the butter over medium heat. Add the mushrooms and saute until they are tender and the juices, if any, have cooked away. (Wild mushrooms release almost no juices.) If the mushrooms seem dry, add a few drops of chicken stock or water and continue to cook until they're nice and tender and any remaining liquid has boiled away. (You want the mushrooms to be dry, almost crisp on the outside.) Add salt and a generous amount of pepper, and set aside.
Spread or spoon about 11/2 teaspoons Camembert on each slice of the toast. Broil for 1 to 2 minutes, or until the cheese has melted (or maybe even disappeared).
To assemble: Reheat the mushrooms if they have cooled, or, if you prefer, keep them at room temperature. Toss the lettuce and eggs with the dressing. Distribute on individual salad plates. Place 4 crostini on each plate, and top each one with about 1 tablespoon of the mushrooms. Sprinkle with a little parsley, and serve.