Prepare the Oven and Pan: Preheat the oven to 350°F (175°C). Grease an 8-inch loaf pan with non-stick cooking spray or line it with parchment paper for easy removal.
Combine Wet Ingredients: In a large mixing bowl, beat together the sugar, eggs, and oil until smooth.Stir in the mashed bananas, Greek yogurt, and vanilla extract until well blended.
Mix Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, whole wheat pastry flour, baking soda, cinnamon, and salt.
Combine Wet and Dry Ingredients: Gradually fold the dry ingredients into the wet mixture. Stir gently until just combined. Avoid overmixing, as it can lead to dense bread. If desired, fold in the toasted walnuts or chocolate chips at this stage.
Bake the Bread: Pour the batter into the prepared loaf pan. Bake in the preheated oven for 50–60 minutes, or until a toothpick inserted into the center comes out clean. If the top begins to brown too quickly, cover it loosely with aluminum foil during the last 15 minutes of baking.
Cool and Serve:
Allow the banana bread to cool in the pan for 5–10 minutes, then transfer it to a wire rack to cool completely. Slice and serve warm or at room temperature.