Preheat oven to 325 F. Line an 11 X 18 inch rimmed baking pan (or jelly roll pan) with parchment paper and lightly oil with canola oil spray
2
Melt the chocolate and butter in a glass bowl in the microwave for 1 1/2 to 2 minutes on high. Stir with a spoon to melt the chocolate completely. Place the beans, 1/2 cup of walnuts, the vanilla extract,and a couple of spoonfuls of the melted chocolate mixture into the bowl of a food processor. Blend about 2 minutes or until smooth. The batter should be thick and the beans smooth. Set aside.
3
In a large bowl, mix together the remaining 1/2 cup of walnuts, remaining melted chocolate mixture, coffee substitute, and salt. Mix well and set aside.
4
In a separate bowl with an electric mixer beat the eggs until light and creamy, about 1 minute. Add agave nectar and beat well. Set aside.
5
Add the bean/chocolate mixture to the coffee/chocolate mixture. Stir until blended well.
6
Add the egg mixture, reserving 1/2 a cup. Mix well. Pour the batter into the prepared pan. Using an electric mixer, beat the remaining 1/2 cup egg mixture until light and fluffy. Drizzle over the brownie batter. use a wooden spoon to pull the egg mixture through the batter creating a marbled effect. Bake for 30-40 minute until the brownies are set. Let cool in the pan completely before cuttin into squared. For the best results refrigerate overnight.