In a medium bowl, whisk together 6 tablespoons of all-purpose flour, cocoa powder, salt, and baking soda.

In another medium bowl, mash the ripe bananas until smooth.

Add sugar, vegetable oil, buttermilk or plain yogurt, vanilla extract, and egg.

Whisk until smooth.

Pour the wet ingredients over the dry ingredients and whisk until just combined.

In a third bowl, toss the chopped walnuts and white chocolate with the remaining 2 teaspoons of flour until evenly coated.

Add the nuts and chocolate to the batter and stir until incorporated.

Scrape the batter into a 7-inch round cake pan insert, metal cake pan, or foil pan, and smooth the top.

Transfer the pan to the air fryer and cook at 310°F (154°C) until a toothpick inserted into the middle of the bread comes out clean, about 30 minutes.

Remove the pan from the air fryer and transfer to a wire rack to cool for 10 minutes.

Unmold the banana bread from the pan and let cool completely on the rack before slicing into wedges to serve.