Preheat your oven to 350°F (175°C). Line a 9x5 inch loaf pan with parchment paper or grease very well with butter or cooking spray.
In a medium sized bowl, whisk together the flour, baking soda and salt and set aside.
In a separate, larger bowl, mix together the melted butter, brown sugar, eggs, vanilla extract and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix the batter.
Stir in the mashed bananas just until combined.
Gently fold in the chocolate chunks but reserve a small handful for the top.
Pour the batter into the prepared loaf pan, spreading it evenly. Sprinkle the top with the remaining chocolate chunks and turbinado sugar for a crunchy topping.
Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, tent the loaf with aluminum foil.
Allow the banana bread to cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely before slicing. Slice and serve warm or at room temperature.