Beat room-temperature butter, white miso paste, granulated sugar, and dark brown sugar on medium-high speed for 3-5 minutes until light and fluffy.
Add egg and vanilla bean paste, beat for 1 minute until incorporated.
Whisk together flour, baking powder, baking soda, and salt in a separate bowl.
Add dry ingredients to butter mixture and mix on low speed until just combined.
Cover dough and chill in refrigerator for at least 3 hours.
Preheat oven to 350F.
Toast white and black sesame seeds in a dry skillet over medium heat for 2-3 minutes until fragrant, then cool completely.
Portion chilled dough into 2-3 tablespoon balls and roll each in toasted sesame seeds until coated.
Place dough balls on parchment-lined baking sheet with 4 inches between them.
Bake for 18-20 minutes, pressing down gently on each cookie with a spatula at the 12-minute mark to encourage crackling.
Cookies are done when edges are golden brown.
Cool on baking sheet for a few minutes, then transfer to wire rack.