Instructions

• Position an oven rack in the lower third of the oven and preheat to 350°F (175°C). Spray a 9×5-inch metal loaf pan with nonstick baking spray and set aside.
• In a large bowl, whisk together 2 cups (240 g) all-purpose flour, 1 teaspoon baking soda, 1 teaspoon baking powder, 1/2 teaspoon ground cinnamon (optional), 1/4 teaspoon ground nutmeg (optional), and 1/2 teaspoon salt until well combined.
• In the bowl of a stand mixer fitted with the paddle attachment or in a large bowl using a handheld electric mixer, beat 1/2 cup unsalted butter (room temperature) until smooth and creamy. Add 1 cup (213 g) light brown sugar (packed) and 2 Tablespoons (24 ml) pure maple syrup and beat on medium speed until light and fluffy, about 3 minutes.
• Add 2 large eggs one at a time, beating well after each addition. If using, beat in 1 teaspoon maple extract.
• In a medium bowl, stir together 1/2 cup (113 g) sour cream (room temperature), 1 and 1/2 cups (405 g) mashed ripe bananas, and 1 and 1/2 Tablespoons vegetable oil until combined.
• With the mixer on low, add the flour mixture to the butter mixture in three additions, alternating with the banana/sour cream mixture and beginning and ending with the flour. Mix just until each addition is incorporated—do not overmix.
• Using a rubber spatula, fold in 3/4 cup walnuts (roughly chopped) until evenly distributed.
• Scrape the batter into the prepared loaf pan and smooth the top. Scatter a few extra walnuts over the top and sprinkle with 1 Tablespoon sparkling sugar (optional), if desired.
• Bake on the lower third rack at 350°F for 65 to 70 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs attached.
• Remove the pan from the oven and place it on a wire rack. Cool the bread in the pan for at least 1 hour, then remove the loaf from the pan and continue cooling on the wire rack until ready to slice and serve.