Bittersweet Chocolate-Mint Mousse
1/8 teaspoon mint extract
Set a large heatproof bowl over a saucepan of barely simmering water. Add the chocolate and butter to the bowl and stir until melted and smooth. Remove the bowl from the saucepan. Whisk in the milk. Let stand for about 15 minutes, stirring occasionally, or until the mixture is cool.
In a medium bowl, using an electric mixer, beat the egg yolks and 1/3 cup of the confectioners’ sugar on medium-high speed, until light and airy. In another medium bowl, using clean beaters, beat the egg whites with the remaining 1/3 cup confectioners' sugar on medium-high speed until soft peaks form. Using a large flexible spatula, fold the egg yolk mixture into the cooled chocolate mixture. Gently fold in the egg white mixture.
Add the cream and the mint extract to the bowl that held the egg whites. Beat with the mixer (no need to clean the beaters) on high speed until thick, soft peaks form. Fold the whipped cream into the chocolate mixture.
Divide the mousse among six to eight dessert cups or bowls. Cover each one with plastic wrap. Refrigerate for at least 2 hours to chill and set the mousse.