Scoop the avocado flesh into your food processor. Blend for 30 seconds until completely smooth, stopping to scrape down the sides once. The mixture should look like pale green frosting with no lumps remaining.

Add the cocoa powder, maple syrup, coconut milk, vanilla, salt, and espresso powder if using. Process for 1 to 2 minutes, scraping down the sides twice, until the mixture is silky and glossy. It will look thin at first but thickens as the cocoa hydrates.

Taste the mousse. If you prefer it sweeter, add maple syrup 1 tablespoon at a time. If it is too thick, thin with 1 tablespoon of coconut milk. The final texture should hold soft peaks when you lift the spatula.

Divide among four glasses, smoothing the tops. Refrigerate uncovered for at least 30 minutes to firm up. The mousse will keep covered for up to 2 days.

Top with a dollop of coconut whipped cream and a sprinkle of cocoa nibs just before serving.