Slow-Cooker Triple Chocolate Brownies

INGREDIENTS

• Nonstick cooking spray
• 1 1/4 cups all-purpose flour (spooned and leveled)
• 1/4 cup unsweetened cocoa powder
• 3/4 teaspoon baking powder
• 1/2 teaspoon coarse salt
• 1/2 cup (1 stick) unsalted butter, cut into pieces
• 8 ounces bittersweet chocolate, chopped
• 1 cup sugar
• 3 large eggs, lightly beaten
• 1 cup walnut halves, coarsely chopped
• 1 cup semisweet chocolate chips (6 ounces)