In a large mixing bowl, beat the butter, sugars, miso, and vanilla until light and fluffy (about 3 minutes).
5 Tbsp (71g) unsalted butter, 2 Tbsp white miso paste, 1/2 cup (100g) light or dark brown sugar, 1/2 cup (100g) granulated sugar, 1/2 tsp vanilla extract
Mix in the egg. Stir in the dry ingredients until almost combined.
1 large egg
Fold in the chocolate until just combined.
4 oz dark chocolate or semi-sweet chocolate
Scoop the cookie dough into a Tupperware container lined with wax paper using a medium cookie scoop or tablespoon. Cover and chill in the fridge for at least one hour or up to 3 days.
When ready to bake, preheat the oven to 350F and line two cookie sheets with parchment paper or silicone baking mats. Place the chilled cookie dough 2" apart onto the prepared baking sheets.
Bake for 10-12 minutes or until the edges are lightly browned. Sprinkle with sesame seeds if using as soon as the cookies come out of the oven.
Notes
Leftover cookies can be stored in an airtight container at room temperature for up to 3 days.