In a large mixing bowl, combine ½ cup of cooled melted butter and ¾ cup of brown sugar. Mix vigorously with a whisk until smooth and glossy.

Add 1 ripe mashed banana, 1 egg yolk, and 1 teaspoon of vanilla extract to the mixture. Blend until fully incorporated.

Sprinkle in a pinch of salt, ½ teaspoon of baking soda, and ½ teaspoon of cinnamon. Stir until evenly distributed.

Gradually fold in 1 cup of all-purpose flour until no dry streaks remain. The dough should be slightly sticky.

Fold in ½ cup of chocolate chips (and optional walnuts if desired). Make sure they are well dispersed.

Cover with plastic wrap and refrigerate for 1 hour.

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

Using a 1.5 oz scoop, portion the dough onto baking sheets, spacing about 2 inches apart.

Bake for 10-12 minutes, watching for golden edges and slightly soft centers.

Allow cookies to cool on the sheet for 2 minutes before transferring to a wire rack.