Preheat the oven to 350°F. Liberally butter a 6 x 3-inch souffle dish or a 9-inch glass pie plate.

Place the chicken in a small saucepan and add enough water to barely cover. Bring to a boil over high heat, then reduce the heat and simmer, uncovered, until the chicken is poached, about 5 minutes. Drain the chicken and set it aside to cool.

Cut the cooked chicken into chunks.

And combine it with ½ cup of the chicken broth in a food processor or blender. Process until smooth.

Separate 3 of the eggs, setting the egg whites and eggshells aside and placing the yolks in a medium-size bowl. Add the remaining whole eggs, the salt, and beat with a whisk until frothy. Add the chicken and another ½ cup of the broth. Blend well. Pour this mixture into the prepared souffle dish or pie plate. Set it in a larger baking pan and add enough water to reach halfway up the inside dish. Bake until the custard is firmly set, about 45 minutes for the souffle dish and 30 minutes for the pie plate. Carefully remove the dish from the water bath and set the custard aside to cool.

Turn the cooled custard out onto a cutting surface. Cut into ½-inch diamond shapes by slicing ½-inch strips on the diagonal, first in one direction, then in the opposite direction. Set aside.

Using the reserved egg whites and shells, clarify the remaining 6 cups broth as directed on page 9.

To serve, divide the custard diamonds evenly among warmed soup bowls. Add a slice of truffle, if using, and slowly pour 1 cup of the broth into each bowl. Pass the grated cheese.