In a food processor mix walnuts and dates until finely ground.
Add in cocoa powder, peanut butter and vanilla extract and mix well.
Line an 8x8 pan with a piece of parchment paper. Use your fingers to press the mixture evenly into the pan.
Optional: sprinkle the brownies with crushed peans (or other nuts), shredded coconut or chocolate chips. Use your fingers to press topping into the top of the brownies.
Cover and refrigerate for at least an hour before cutting.
To make a 9x13 pan double the recipe