Preheat the oven to 350˚F and line 2 baking sheets with parchment paper.
In a medium bowl large enough to hold all of the ingredients, stir together the melted coconut oil, sugars, eggs, and miso. Either a large metal spoon or a whisk work fine for this.
In a small bowl, whisk together the flour, baking powder and salt. Add to the bowl containing the coconut oil, and mix together with a large metal spoon. The batter will thicken both from the addition of the dry ingredients, and the gradual hardening of the coconut oil as it cools. Fold in the chocolate pieces.
Use a medium-size ice cream scoop and scoop out the batter to form cookie balls on the prepared baking sheet. Very lightly sprinkle a little salt on top. You just need a few grains of salt on each cookie. Bake for 10-12 minutes. I bake one sheet at a time since they're not in the oven for long. If you bake both cookie sheets at the same time, add 1-2 minutes to the baking time, and switch around the sheets half-way through baking.
Slide the parchment paper with the cookies onto a cooling tray.