In a large mixing bowl, combine melted butter (or oil), brown sugar, and mashed banana. Mix until smooth and well combined.

Add the egg yolk and vanilla extract. Mix until fully incorporated.

Stir in flour, baking soda, salt, and cinnamon. Mix just until no streaks of flour remain.

Fold in the chocolate chips evenly throughout the dough.

Cover the bowl and let the dough rest for 15 minutes to hydrate while the oven preheats.

Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.

Scoop 1-ounce portions of dough and place them 2 inches apart on the prepared baking sheet. The dough will be slightly soft.

Bake for 10–11 minutes, until edges are set and the centers are slightly underbaked.

Let the Banana Bread Chocolate Chip Cookies cool on the pan before transferring. They will firm up as they cool.