In a large mixing bowl, combine ½ cup of cooled melted butter and 1 cup of brown sugar, mixing until fully blended. Then add 1 ripe mashed banana, 1 egg yolk, 1 teaspoon of vanilla extract, a pinch of salt, ½ teaspoon of baking soda, and ½ teaspoon of cinnamon. Stir until smooth.

Gradually fold in 1 ½ cups of all-purpose flour until just combined; then gently fold in 1 cup of chocolate chips and ½ cup of walnuts if using.

Cover the bowl with plastic wrap and refrigerate the dough for 1 hour.

Preheat your oven to 350°F (175°C) and line your baking sheets with parchment paper.

After chilling, scoop dough onto prepared sheets, leaving 2 inches between each cookie.

Bake for 10-12 minutes until edges are golden brown and centers are soft.

Cool on the baking sheets for 2 minutes before transferring to wire racks to cool completely.