Preheat oven to 350 degrees. Line several cookie sheets with parchment paper or silicone mats.
Place 4 oz of the butter in a saucepan. Melt over medium heat, swirling occasionally, until it starts to turn brown and smells nutty. Do not let the butter get too dark or it will burn. Strain butter into a clean bowl.
Place remaining 4 oz butter, sugar, and brown sugar in bowl of stand mixer. Beat with paddle attachment until light colored and fluffy.
Add browned butter and beat to combine.
Add in egg and beat to combine.
Add in vanilla and beat to combine.
Combine flour, ground oats, baking soda, baking powder, and salt in a medium bowl.
Add to mixer and beat just until combined.
Add in chocolate and mix just to distribute evenly.
Place approximately 2 in round balls on prepared sheets. Press down lightly to flatten.
Sprinkle tops with sea salt.
Bake for 12 to 14 minutes, rotating once, until edges are brown and center looks just firm.
Remove from oven and let cool on wire racks before removing and eating.