1. Place walnuts in food processor and blend on high until the nuts are finely ground.
2. Add the cacao and salt. Pulse to combine.
3. Add the dates one at a time through the feed tube of the food processor while it is running. What you should end up with is a mix that appears rather like cake crumbs, but that when pressed, will easily stick together (if the mixture does not hold together well, add more dates).
4. In a large bowl (or the pan you plan on putting the brownies in), combine the walnut-cacao mix with the chopped almonds. Press into a lined cake pan or mold. Place in freezer or fridge until ready to serve (it is also easier to cut these when they are very cold). Store in an airtight container.