First, make the crust. Add all crust ingredients, except almond milk, to a food processor and pulse 7-10 times until the almonds are broken up. Then process on low until crumbly. Pour in the almond milk and continue to process until the mix starts clumping together. The mix should easily stick together when you squeeze it between your fingers. Transfer the crust to a bowl and set aside.
Line 4 (3-4 inch) tart pans or molds with either parchment paper or plastic wrap, making sure to line up the sides of the pans as well. This keeps the tarts from sticking. You can also use a 6 to 8-inch tart pan. Divide the crust among the tarts and, one tart at a time, begin pressing the crust into the tart and working it a little bit up the sides. The crust should be no less than ½ inch thick.If using an 8-inch tart pan, you might not have enough crust to work up the sides of the pan. This is ok. Just press the crust into the bottom of the pan. Place the crusts-lined pans in the freezer for 20 minutes to set.
Next, make the mousse. Add all the mousse ingredients, except the cocoa powder, to a blender and blend on high until the mixture is combined but not smooth. Now add the cocoa powder and blend again until smooth.
Remove the crusts from the freezer. Remove the tart crusts from the pans/mold and gently peel the parchment or plastic wrap off the crusts and transfer to a serving plate. Fill each tart with the chocolate filling. Garnish with fresh berries, hemp seeds and cacao nibs, if using, and serve!