Place chocolate 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 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 whites, 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 for at least 4 hours. Garnish with whipped topping and grated chocolate, if desired.