To make these cookies, start by preheat your oven to 350 F.
Next, brown the butter. Melt the butter in a small/medium-sized saucepan over medium heat, swirling the pan occasionally, until the butter turns golden brown and starts to smell incredible. This will take about 3-5 minutes. Just make sure to keep a close eye on it, because when the butter starts to foam up, it can go from brown to burnt in a few seconds.
Once the butter has been browned, remove the pan from the heat, and pour the browned butter into a small bowl. Allow it to cool completely – this is important.
In a large mixing bowl or the bowl of a stand mixer, add the cooled brown butter and the sugars, and mix them until they’re fully creamed.
Next, add in the egg, egg white and the vanilla extract. Mix until just combined.
Then, add in the flour, baking soda, salt, oats and chocolate, and mix until just combined.
Line a baking sheet with parchment paper and use a cookie scoop to form 12-16 cookies and line them on your baking sheet, keeping at least 2 inches of space in-between.
Then, transfer the cookies to your oven and bake them for 8-10 minutes; if you like a soft cookie like I do, I recommend baking them for 8-9 minutes.
Once they're done, remove them from the oven and add a touch of flaky salt, if desired.
Let the cookies cool, then serve and enjoy!