Preheat the oven to 350ºF (165ºC). Line the bottom an 8 x 4-inch or a 9 x 5-inch loaf pan with parchment paper. Grease and flour the insides.
In a medium-sized bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon and nutmeg until well blended.
In a large bowl, whisk together the brown sugar, oil, eggs, sour cream and vanilla until creamy and well blended. Stir in the bananas until incorporated. Mix in the flour mixture just until combined. Do not over mix. Stir in the 1/2 cup of pecans if using. If using chocolate chips, set aside 1/4 cup (43g) for the top and toss the remaining 1 cup (170g) of chocolate chips with 1 teaspoon of flour, then mix them into the batter.
Transfer the batter to the prepared loaf pan. Sprinkle the loaf with the chopped pecans or 1/4 cup (43g) of chocolate chips. Bake until a toothpick inserted into the center of the loaf comes out clean, about 40-50 minutes. Cool in the pan for 10 minutes, then remove the loaf from the pan and transfer it to a cooling rack to cool completely.