Preheat your oven to 350°F (175°C).

Mash the ripe bananas in a mixing bowl until smooth, about 1 to 2 minutes.

Add melted butter (or vegetable oil) and light brown sugar to the mashed bananas. Mix until smooth and glossy, about 2 minutes.

Stir in one egg yolk and a splash of vanilla extract. Mix until well combined, about 1 minute.

In a separate bowl, whisk together all-purpose flour, baking soda, cinnamon, and salt.

Gradually add the dry ingredients to the wet mixture and stir gently until just combined, about 1-2 minutes.

Fold in chocolate chips gently into the dough, using a spatula.

Cover the dough and let it rest at room temperature for about 15 minutes.

Drop 1-inch balls of dough onto a lined baking sheet, spacing them about 2 inches apart. Bake for 10-11 minutes until edges are set.

Cool cookies on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.