Beat the aquafaba with a stand mixer or hand mixer. When it starts to foam, add the sugar to help stabilize the chickpea 'whites'.

Melt the dark chocolate over low heat, then let it cool to room temperature.

Gently fold the melted chocolate into the whipped aquafaba. Be sure to scrape the bottom of the bowl, as the chocolate tends to sink.

Pour the mixture into small ramekins, sprinkle with sea salt flakes, and refrigerate for at least 4 hours to set the mousse.