Brown the butter in a pan over medium heat until browned and nutty. Stir in the miso paste and cool for 5 minutes.
Whisk the sugar into the butter then whisk in the egg, egg yolk, and dry ingredients. Finally add the chopped chocolate.
Fold in the chopped chocolate until just combined.
Scoop and chill for 15 minutes then bake at 350 for 11-12 minutes.