Heat the oven to 350 degrees. Lightly grease a 9-by-5-inch loaf pan with butter.
In a medium bowl, whisk the flour, baking soda, baking powder and salt to combine.
In a large bowl, mash the bananas coarsely using a fork. They should be fully broken apart, but it’s OK if some larger lumpy pieces remain. Whisk in the melted butter, yogurt, sugar, eggs and vanilla until well combined.
Add the flour mixture to the banana mixture and stir to combine using a silicone spatula or wooden spoon. Scrape the sides and base of the bowl well to make sure the mixture is uniformly combined.
Add in the chocolate chips, nuts and raisins to the batter.
Pour the batter into the prepared pan and spread into an even layer. Sprinkle with the reserved 2 tablespoons chocolate chips.
Transfer the pan to the oven and bake until the edges of the loaf start to pull away from the edge of the pan, and a tester inserted into the center comes out with just a few moist crumbs attached, 50 minutes.
Transfer from the oven to a cooling rack and run a thin knife around the edge of the banana bread to separate it from the pan. Let cool in the pan for 10 minutes before unmolding and cooling completely.