Preheat the oven to 350F. Line two baking sheets with parchment paper.
Place ½ cup (1 stick) of butter into a medium saucepan over medium heat. Let the butter cook while occasionally stirring to ensure the butter is cooking evenly.
Cook the butter until it is a deep golden brown color and smells nutty and toasted, about 5 -7 minutes. Remove the pan from the heat. Let the butter cool to room temperature.
In a medium bowl, whisk together the flour, and baking soda. Set aside
2 ½ cups all purpose flour, 1 teaspoon baking soda
In the bowl of a stand mixer fitted with a paddle attachment, combine the remaining ½ cup (1 stick) of butter and brown sugar. Beat on medium speed until light and fluffy, about 3-5 minutes.
1 cup light brown sugar
Beat in the miso paste and vanilla, until well combined, about 1 minute.
3 tablespoons white miso paste, 2 teaspoons pure vanilla extract
Beat in the granulated sugar and the cooled brown butter and beat until light and creamy about 2 minutes.
½ cup granulated sugar
Scrape down the sides of the bowl, then add the egg and egg yolk and mix on medium speed for an additional minute.
1 large egg, 1 large egg yolk
On low speed, beat in the flour mixture until just combined.
Add the chocolate chips and mix to combine.
1 ½ cups semi sweet or bittersweet chocolate chips
Scoop the dough with a medium size/2 tablespoon/1oz ice cream scoop onto prepared baking sheets, placing the dough balls 2" apart on the baking sheets.
Chill the cookies in the refrigerator for 1 hour.
Sprinkle with sesame seeds if using. Bake for 13-15 minutes or until the bottom edges are lightly brown and the tops look just set.
sesame seeds (optional)
Remove from the oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.