Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan, or line with parchment paper leaving an overhang on the long sides for easy removal.

In a medium bowl, whisk together the all-purpose flour, baking soda, salt, and ground cinnamon (if using). Set aside.

In a large mixing bowl, mash the ripe bananas with a fork or potato masher until mostly smooth with a few small lumps remaining.

Add the melted butter, granulated sugar, and brown sugar to the mashed bananas. Stir until well combined.

Stir in the lightly beaten egg, vanilla extract, and sour cream (or Greek yogurt) until just combined. Do not overmix.

Gradually add the dry ingredients to the wet ingredients, mixing with a spatula until just combined. Be careful not to overmix; a few streaks of flour are okay.

Gently fold in the diced fresh strawberries and white chocolate chips (if using) until evenly distributed.

Pour the batter into the prepared loaf pan and spread evenly.

Bake for 55-65 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean or with moist crumbs, but no wet batter. If the top starts browning too quickly, you can tent it loosely with aluminum foil for the last 15-20 minutes of baking.

Once baked, remove the loaf pan from the oven and let it cool in the pan for 10-15 minutes. This helps the bread set and prevents it from crumbling.

Carefully lift the bread out of the pan using the parchment paper overhang (if used) or invert onto a wire rack to cool completely before slicing and serving. Cooling completely is crucial for the best texture.