In a small saucepan over low to medium heat, add your unsalted butter and stir slowly and consistently. The butter will melt, then foam, then you will start to see those gorgeous brown bits forming at the bottom and smell that nutty caramel aroma. As soon as it turns golden brown, remove from heat. Let it cool for 10 minutes.

Once cooled, transfer your brown butter to a large mixing bowl and add your light brown sugar. Mix together for about 1 to 2 minutes until fully combined.

Add in your mashed banana and stir until incorporated. The mixture might look a little broken at first, just keep stirring.

Add in your egg, egg yolk, and vanilla bean paste, then mix again until smooth and creamy.

In a separate bowl, whisk together your all purpose flour, old fashioned oats, cornstarch, baking powder, cinnamon, and salt.

Fold the dry ingredients into the wet ingredients until just combined. Do not overmix.

Coarsely chop your dark chocolate bar, making sure to leave a mix of small and big chunks. This is what gives you those incredible gooey pockets throughout.

Add your chopped dark chocolate and semi sweet chocolate chips to the dough and fold in gently until evenly distributed.

Cover the dough and refrigerate for 30 minutes. This step is essential for the perfect texture, do not skip it.

Preheat your oven to 350 degrees F and line a baking sheet with parchment paper.

Scoop the dough into 14 equal sized balls, about 2 tablespoons each. Place on your prepared baking sheet leaving room for spreading.

Bake for 9 to 11 minutes, or until the edges are just set and the centers still look slightly underdone. They will continue to bake on the pan.

As soon as they come out of the oven, take a biscuit cutter or small bowl slightly larger than the cookie and wiggle it around each cookie to create a perfect circle shape. This step is totally cosmetic but it makes them look SO professional. You can absolutely skip this if you do not care about the shape.

While the cookies are still warm, press a few extra chocolate chunks on top and sprinkle with flaky sea salt. This makes them STUNNING.

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