On medium high heat, melt the butter in a saucepan until it turns brown. Once the butter starts to brown, take it immediately off the heat and let it rest to cool.
When the butter is slightly cool, pour the butter into a mixing bowl and add the brown and white sugar. Mix until well combined.
Add the other wet ingredients (vanilla extract, miso, and egg) into the bowl of sugar and butter and mix until it is a uniform and glossy mixture with no lumps.
In a separate bowl, sift the all-purpose flour, salt, and baking soda together and whisk to combine.
Fold in half of the dry ingredients into the bowl of wet ingredients with a rubber spatula. Once it is well combined, fold in the remaining half of the dry ingredients. Stir until it becomes a uniform dough.
Gently fold in the chocolate chips into the dough mixture until it is well combined.
Scoop the cookie dough into balls and let them sit in the fridge for at least 3 hours (preferably overnight).
Preheat your oven to 350 degrees Fahrenheit.
Place the chilled cookie dough balls onto an aluminum baking tray lined with parchment paper or baking slipmat. Press the cookie dough into a thick disk shape (like a hockey puck) to allow it to spread.
Bake the cookies for 11-13 minutes or until the edges are golden brown and the center is puffed up. Be careful not to overbake! We want the center to be chewy.
Once the cookies are baked, pull them out of the oven and firmly tap the tray several times onto a flat surface to spread and flatten the cookies. Afterwards, use a slotted spatula to carefully transfer the cookies over to a wire rack to cool.
Sprinkle some flaky sea salt on top of the cookies for a finishing touch.