Preheat oven to 350°F. Line two baking sheets with parchment paper and grease lightly with cooking spray. Set aside.

Whisk together the flour, baking powder, salt and sugar in a large bowl. In a separate bowl, whisk together the mashed banana, egg, oil and vanilla until smooth.

Pour the wet ingredients into the dry ingredients along with the chopped walnuts. You’ll want the walnuts to be roughly chopped. They don’t all have to be uniform in size just make sure they’re fairly small pieces.

Transfer the dough to a well-floured work surface and divide in half. Then with well-floured hands, shape each half into a log that is about 8-inches in length. Transfer the logs to a baking sheet that has been lined with parchment and lightly greased with cooking spray. Flatten out each log to about 1/2-inch thick and then sprinkle the tops with more chopped up walnuts.

Bake for 15 minutes. Remove from the oven and let cool for about 10 minutes. Meanwhile, lower the temperature to 250°F. Slice the logs on a diagonal into about 10 to 12 slices per log, depending on how thick you make your biscotti. Return to the baking pan in a single layer, cut-side down, and bake for 15 minutes. Flip the biscotti over and continue to bake for another 10 minutes.

Remove from the oven and let cool on the pan for about 10 minutes, before transferring them to a wire rack to cool completely and dry out a bit more. Serve and enjoy!