Preheat the oven to 350F. Line an 11 x 18 inch rimmed baking pan with parchment paper and lightly oil with canola oil spray.
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, 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.
In a large bowl, mix together the walnuts and remaining melted chocolate mixture, then set aside.
In a separate bowl, with an electric mixer beat the eggs until light and creamy, about 1 minute. Add the sugar and beat well. Set aside.
Add the egg mixture to the bean/chocolate mixture. Mix well.
Pour the batter into the prepared pan. Bake for 30 to 40 minutes, until the brownies are set. The top should be shiny and a toothpick inserted should come out clean.
Let cool in the pan completely before cutting into squares. Refrigerator or freeze.