Dark Chocolate Brownies - Ellie Krieger

Ingredients

• Nonstick cooking spray
• 8 ounces bittersweet chocolate, coarsely chopped
• 2 tablespoons unsalted butter
• 1 cup whole-grain pastry flour or whole-wheat flour
• 1/4 cup unsweetened natural cocoa powder
• 1/4 teaspoon salt
• 1/4 teaspoon baking soda
• 4 large eggs
• 1 cup packed light brown sugar
• 1/2 cup plain low-fat yogurt
• 1/4 cup canola oil
• 2 teaspoons vanilla extract
• 3/4 cup chopped walnuts, optional