In a medium bowl, whisk together the flour, baking powder and baking soda.
In a stand mixer with the paddle attachment, beat the butter, brown sugar and white sugar on medium-high until well combined, about 3 minutes.
Add the peanut butter, miso and oil, then beat, scraping the bowl once or twice, until light and fluffy, about 2 minutes.
Add the egg and vanilla and beat again, then scrape the bowl.
With the mixer on low, gradually add the flour mixture.
Mix, scraping the bowl as needed, just until the dough is evenly moistened, 1 to 2 minutes.
Using a spatula, mix the dough by hand to ensure no pockets of flour remain; the dough with be very soft.
Press a sheet of plastic wrap against the surface of the dough and refrigerate for at least 2 hours or up to 24 hours.