Creating a luscious coffee mousse is not only rewarding but straightforward. Follow these steps to whip up this stunning dessert:

1. Prepare Coffee Mixture: In a small bowl, mix the cooled brewed coffee, coffee liqueur, and granulated sugar until dissolved. Set aside.
2. Melt Chocolate: In a microwave-safe bowl, melt the semi-sweet chocolate chips. Heat in 20-second intervals, stirring in between until smooth. Allow it to cool slightly.
3. Whip Egg Whites: In another bowl, whip the egg whites with a pinch of salt until soft peaks form. This will add a light and airy texture to the mousse.
4. Prepare Cream: In a separate bowl, whip the heavy cream until soft peaks form. Be careful not to overwhip.
5. Combine Egg Yolks and Chocolate: In a bowl, whisk the egg yolks into the melted chocolate until well blended. Add the coffee mixture and vanilla extract, mixing until thoroughly combined.
6. Fold in Egg Whites: Carefully fold the whipped egg whites into the chocolate mixture, being gentle to maintain volume.
7. Fold in Whipped Cream: Next, fold in the whipped heavy cream until the mixture is smooth and well-combined, preserving the lightness.
8. Chill the Mousse: Spoon the mousse mixture into individual cups or ramekins. Cover and refrigerate for at least 25 minutes to firm up.
9. Serve: Once chilled, your coffee mousse is ready to serve!