Place chocolate chips and tofu in a food processor or blender, and process 2 minutes or until smooth.
Place salt and egg whites in a medium bowl, and beat with a mixer at high speed until stiff peaks form. Combine sugar and 1/4 cup water in a small saucepan; bring to a boil. Cook, without stirring, until candy thermometer registers 238°. Pour the hot sugar syrup in a thin stream over egg white mixture, beating at high speed. Gently stir one-fourth of meringue into the tofu mixture; gently fold in remaining meringue. Spoon 1/2 cup mousse into each of 8 (6-ounce) custard cups. Cover and chill at least 4 hours. Garnish with whipped topping and grated chocolate, if desired.
Tofu is the key to making this dessert light and creamy, but you won't be able to taste it. Be sure to use plain tofu for the best results.