Place the avocado, cocoa powder, maple syrup, and vanilla in your food processor bowl. I use the "chop" setting in this mini food processor.
Process until smooth and creamy, for about one minute, stopping once to scrape the sides of the bowl with a spatula if needed.
When done, the mousse should be thick and creamy. Taste it and add more cocoa powder or sweetener if needed.
Allow the mousse to rest at room temperature for 30 minutes before serving. THis allows the flavors to meld.
Video
Notes
No, you can't taste the avocado. :) It adds volume and creaminess, not flavor.
You can replace the maple syrup with stevia (follow the package conversion instructions) and add ½ cup of water. This version is shown in the video above. However, this could result in a slightly bitter aftertaste, espcially if you're not used to stevia.
The nutrition info assumes that this sugar-free maple syrup was used, and the sugar alcohols were subtracted from the carb count. If using real maple syrup, each serving has 216 calories, 38 grams of carbs, 25 grams of sugar, 7 grams of fiber, 9 grams of fat (2 grams saturated), 3 grams of protein, and 9 grams of sodium.
The avocado should be a Haas variety and very ripe, but not overripe - the flesh should be creamy and green. Brownish flesh can taste off and be bitter.
The cocoa powder must be Dutch-processed (processed with alkali). Natural cocoa powder is too acidic.
Make-ahead and storage: Because it contains raw avocado, I suggest making this mousse on the day you plan to eat it. You can make it a few hours in advance and refrigerate it covered. But I wouldn't try to keep it any longer than that. I don't recommend freezing this mousse, as the texture will be off after thawing.