Place 1 cup walnuts and 1 cup almonds in food processor and process until finely ground (amounts as original recipe is written // adjust if altering batch size).
Add the cocoa powder or cacao, espresso powder, and sea salt. Pulse to combine and then transfer to bowl and set aside.
Add the dates to the food processor and process until small bits remain. Remove from bowl and set aside.
Add nut and cocoa mixture back into food processor and while processing, drop small handfuls of the date pieces down into the food processor spout (or turn off food processor every few pulses, adding date pieces in a little at a time). Process until a dough consistency is achieved, adding more dates if the mixture does not hold together when squeezed in your hand.
Add the brownie mixture to a parchment-lined cake pan (8 x 8-inch or 9 x 13-inch) and add remaining roughly chopped walnuts (1/2 cup as original recipe is written). Toss to combine and evenly distribute, and then press down with you hands until it is flat and firm.
Place in freezer or fridge to chill before cutting. Store in an airtight container to keep fresh. Will keep in the fridge for at least 2 weeks and in the freezer for at least 2 months.
Notes
*Nutrition information is a rough estimate based on the lesser amounts of dates and espresso powder.