In a bowl, mix the melted butter with the miso until well combined.
Add the white sugar, brown sugar and vanilla extract, mixing until fully incorporated.
Add the egg, and mix again.
Incorporate the dry ingredients: flour, baking powder, salt, chocolate chips and chopped chocolate, mixing until a uniform dough forms.
Cover the dough and refrigerate for at least 1 to 3 hours.
Preheat the oven to 350°F (180°C).
Line a baking sheet with parchment paper.
Use a #20 scoop to form dough balls and place them on the baking sheet, leaving space between each.
Bake for 15 minutes or until the edges are golden brown.
Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.