Step 1: Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.

Step 2: In a large bowl, mix the mashed bananas, melted butter, sugar, egg, and vanilla extract until well combined.

Step 3: In a separate bowl, whisk together the flour, baking soda, and salt.

Step 4: Gradually add the dry ingredients to the wet ingredients, stirring until just combined.

Step 5: Gently fold in the raspberries and dark chocolate chunks.

Step 6: Pour the batter into the prepared loaf pan and smooth the top with a spatula.

Step 7: Bake for 50-55 minutes, or until a toothpick inserted into the center comes out clean.

Step 8: Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.