Preheat the oven to 350°F (175°C) and prepare a muffin tin with liners.

In a mixing bowl, combine mashed bananas, Nutella, vegetable oil, eggs, and vanilla extract.

In a separate bowl, mix together flour, sugar, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture and stir until just combined. Fold in chocolate chips if using.

Divide the batter evenly among the muffin cups and bake for 20 minutes or until a toothpick inserted comes out clean.

Allow muffins to cool for a few minutes before transferring to a wire rack to cool completely.