In a stand mixer fitted with the paddle attachment, add the butter, granulated sugar, and brown sugar and mix until fluffy, a few minutes. Scrape the sides of the bowl as needed with a spatula.

Add the miso (if using) and peanut butter and mix for a few seconds before adding the flour, baking powder, and baking soda. Mix until a dough forms. Again, scrape the sides of the bowl as needed. If the dough feels too dry and crumbly, add a little more peanut butter, about up to 1 to 2 tablespoons (16 to 32 g). Cover the dough with plastic wrap or transfer to an airtight container and refrigerate for at least 30 minutes to 1 hour. This cookie dough can also be stored in the refrigerator for a few days, or up to 5 months in the freezer.

About 20 to 30 minutes before baking, preheat the oven to 350°F (180°C) with a rack in the center. Line a baking sheet with parchment paper or a silicon mat.

I like these cookies big and chonky, like ping-pong balls, about 1.3 ounces (36 g) each or more than a heaping tablespoon. You’ll have about 12 to 15 portions; roll each into a ball between your palms. You may need to compact and squeeze the ball together a bit to keep its shape.

Press a whole peanut into the center of each cookie ball. Transfer the cookie balls to the baking sheet, giving each space. While they won’t expand much while baking, they will need consistent airflow to bake nicely. Brush all the tops with the egg wash.

Bake until the tops shine and the edges are browner, about 16 to 18 minutes.

Allow the cookies to cool on the baking sheet and enjoy them warm.