Place cooked sweet potato and peanut butter in a food processor. Process until smooth and, then add cocoa powder, maple syrup, and orange zest, and blend again until smooth. 

Place chickpea brine in a clean bowl. Add lemon juice and whip with a hand mixer until you achieve stiff peaks (this can take around 3-6 mins) – you should be able to invert the bowl, and the whipped brine should not move an inch.

Fold whipped chickpea brine into the chocolate and mix until well combined. The mixture will deflate slightly.

Spoon the mixture between 4 small serving glasses and place in the fridge for 8 hours (or overnight) for the mousse to set.