Melt ingredients: Add the dark chocolate to a medium heatproof bowl with the soy cream and place on top of a saucepan with a little water in the bottom (called a double boiler or bain marie). Gently heat until the chocolate has melted, stirring every so often.
Carefully remove the bowl from the water bath and stir in the pure maple syrup, vanilla extract, and salt. Set aside to cool slightly for 15-20 minutes.
Whip aquafaba: To a clean large bowl or stand mixer bowl add the aquafaba and lemon juice. Use an electric whisk/stand mixer to beat for 10-12 minutes until it has stiff peaks, and you can comfortably hold the bowl upside-down over your head.
Fold: Gently fold one-third of the whipped aquafaba into the cooled melted chocolate mixture using a rubber spatula. Fold the remaining aquafaba in 2 parts, until just incorporated into the mousse, but don't be tempted to overmix as this will knock out the air.
Set: Divide the mousse between small ramekins, serving glasses, or small bowls. You can use an ice cream scoop to help measure even portions. Place the mousse in the fridge for at least 4 hours or overnight if preferred.
Serving: Top with vegan whipped cream just before serving.
