Preheat the oven to 350°F (175°C) and line an 8x8 inch square baking pan with parchment paper.
In a large bowl, mash the bananas until smooth, then whisk in the nut butter, maple syrup, and vanilla extract until well combined.
Stir in the rolled oats, cinnamon, and salt until the oats are fully incorporated and moistened.
Fold in the dark chocolate chips evenly throughout the batter.
Transfer the mixture to the prepared baking pan and press down firmly with a spatula to create an even layer.
Bake for 20 to 25 minutes or until the edges are golden and the center is firm to the touch.
Allow the bars to cool completely in the pan to ensure they set properly before slicing.
Lift from the pan using the parchment paper and cut into 12 bars.