Cut the avocados in half, remove the pits, and scoop the flesh into a blender or food processor.
Add the cocoa powder, powdered sweetener, heavy cream, almond milk, vanilla, salt, and espresso powder if using.
Blend until the mixture becomes completely smooth. Stop once or twice to scrape down the sides of the container.
Taste the mousse and add a little more sweetener or almond milk if needed. Blend again until the texture is creamy and even.
Divide the mousse among four small glasses or bowls. Cover and refrigerate for at least 30 minutes.
Serve chilled with sugar-free whipped cream or a few fresh raspberries, if desired.
