Preheat oven to 350°F (180°C). Spray or brush an 8-inch (20 cm) square baking pan with vegetable oil and line bottom and sides with parchment paper, leaving overhang; set aside. Melt butter and chocolate in double boiler, stirring until smooth. Remove from heat. Mix in sugar completely then stir in eggs, one at a time. Set aside.
Using a food processor, purée beans until smooth. Stir beans into chocolate mixture until well blended. Sift together flour, cocoa and salt. Stir flour mixture into chocolate mixture; beat vigorously until batter is no longer grainy, about 1 minute.
Stir 1/2 cup (125 mL) nuts into batter and transfer to prepared pan. Sprinkle remaining nuts over top. Bake until a toothpick inserted in centre comes out clean but brownies are still slightly fudgy in centre, about 45 minutes. Transfer pan to a wire rack; let cool completely. Transfer brownies to a cutting board using parchment paper. Cut into 12 portions. Store in airtight container.
DISCLAIMER. As product ingredients occasionally change, customers diagnosed with celiac disease or gluten sensitivities, or those wishing to avoid gluten-containing products, should be careful to always verify the gluten-free status of a product by checking the label and by consulting the Pocket Dictionary – Acceptability of Foods & Food Ingredients for the Gluten-Free Diet, 2012 edition, Canadian Celiac Association. The information provided is not a substitute for professional medical advice. If you have specific needs, please see your health-care provider.