In a large mixing bowl, blend together 1/4 cup of mashed overripe banana, melted unsalted butter or vegetable oil, and 1/2 cup of light brown sugar. Use a whisk or fork to incorporate these wet ingredients until smooth and creamy, ensuring no lumps remain. This should take about 2-3 minutes, creating a wonderfully sweet banana mixture as your base.

Next, mix in one egg yolk (or 1.5 teaspoons of ground flaxseed combined with 2 tablespoons of water for a vegan option) along with 1 teaspoon of pure vanilla extract. Stir vigorously for another minute until fully combined.

Sift together 1 cup of all-purpose flour, 1/2 teaspoon of baking soda, 1/2 teaspoon of ground cinnamon, and a pinch of salt. Gradually fold in the dry ingredients into the wet ingredients until no flour streaks are visible, taking care not to overmix.

Gently fold in 3/4 cup of chocolate chips using a spatula. Cover the bowl with plastic wrap and let it rest for about 15 minutes.

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

Use a cookie scoop or spoon to portion out 1-inch balls of dough onto the prepared baking sheet with about 2 inches of space between each mound.

Bake for 10-11 minutes until the edges are set but the centers remain slightly underbaked.

Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack.