Easy Chocolate Mousse

1 Sprinkle the gelatin on the liqueur in a small bowl and set aside.
2 Combine the milk and 1/4 cup of the sugar in a small saucepan and whisk to mix. Place over medium heat and bring to a simmer.
3 Meanwhile, whisk the eggs in a small bowl. When the milk boils, whisk about a third of the milk into the eggs. Return the remaining milk to a boil over low heat then whisk in the egg mixture. Continue whisking until the mixture thickens slightly. Don't let it boil or the eggs will scramble. Remove from the heat and quickly whisk in the gelatin mixture.
4 Whisk in the chocolate and continue whisking until the chocolate is melted and the mixture is smooth. Scrape it into a medium bowl and cool it to room temperature.
5 To make the meringue, half-fill a medium saucepan with water and bring it to a boil over medium heat. Regulate the heat so that the water simmers gently but isn't boiling violently. Combine the egg whites, salt, and the remaining 1/2 cup sugar in the heatproof bowl of an electric mixer, whisking by hand just to mix. Place the bowl over the pan of water and whisk gently until the egg whites are hot (140 degrees on an instant-read thermometer) and the sugar is dissolved. Place the bowl on the mixer with the whisk attachment and whip on medium speed until the meringue is cooled (it doesn't have to come all the way down to room temperature) and increased in volume.
6 Fold the meringue into the chocolate mixture.
7 Divide the mousse among the prepared glasses and refrigerate until set, 3 to 4 hours.