There's nothing better than chocolate, right? Wrong. It gets even better when it is paired with mint! This mousse is borderline sinful, it's so delicious, and it really hits the spot when you're craving something sweet that isn't necessarily cake. Beware, though - you may find yourself reaching for more than one serving!
Melt the chocolate in a double boiler. Add the strong coffee to the melted chocolate and stir to combine. Let the mixture cool, then beat the butter and peppermint extract into the chocolate.
Separate the whites and yolks of each egg. Add the egg yolks to the chocolate mixture, one at a time, beating to combine in between additions.
In a cold bowl set over a second bowl of ice, whip the cream until it forms soft peaks. Set aside. In a large bowl, beat the egg whites until they form soft peaks as well. Add the sugar, a little at a time, to the egg whites and beat to combine between additions. When all the sugar has been added, beat until the egg whites form stiff peaks.
Add the chocolate mixture to the egg whites in three or four smaller portions, beating to thoroughly combine between additions. Fold the cream into the chocolate and egg white mixture. Whisk to fluff the mousse, then divide among several small portion bowls. Transfer to the refrigerator to set for a couple of hours. If making more than a few hours in advance, cover the top of the bowl with plastic wrap before transferring it to the fridge.
Serve the mousse with whipped cream, sprinkles, and a mint sprig for garnish if desired.