Add the walnuts, cacao powder and salt to your food processor and blitz for a minute. Add the dates and vanilla extract and blend again until the ingredients stick together to form a dough. Press the mixture into an 8” tin lined with parchment paper using a spatula. Set aside.
Heat the coconut milk, coffee and vanilla in a saucepan until lightly simmering, whisk well. Remove from the heat and add the chocolate, allow to sit for 5 minutes before stirring until the chocolate is melted through. Add the maple syrup and stir well. Set aside and allow to come to room temperature.
To a clean large bowl add the aquafaba and cream of tartar. Use an electric whisk/stand mixer to beat for about 8 minutes until stiff. Use a spatula to carefully fold the whipped aquafaba into the cooled chocolate mixture, one large spoonful at a time. Once all of the ingredients have been incorporated, transfer the mousse to the baking tin and freeze for 1 hour or until the surface is solid.
For the coulis add the frozen raspberries, maple syrup and lemon juice to a saucepan and simmer for 25-30 minutes stirring occasionally, until the mixture has reduced by about half. Pass the mixture through a sieve to remove the seeds and allow the to cool to room temperature. Once cooled spread the coulis on top of the mousse and return to the freezer to set completely overnight (or minimum 4 hours).
Melt the chocolate over a double boiler (bain-marie).
Cut the brownies into 16 portions using a sharp knife. (heat the knife in boiling water to make it easier to cut the frozen bars). Place the brownies back in the freezer and one-by-one take them out and dunk them in the melted chocolate using 2 forks. Sit the coated brownies on a sheet of parchment paper. Garnish with a drizzle of chocolate, freeze dried raspberries and flaky sea salt.
Serving and Storage
Allow to defrost for 15-20 minutes before eating and store in the fridge in an airtight container or freeze extra portions for later!