Preheat the oven to 350ºF (175ºC). Position an oven rack to the center position of the oven. Line 2 large half-sheet baking pans with foil (dull side up) or parchment paper. (See note 3 for more notes about baking on foil vs parchment paper.)
Grab a large #16 ice cream scoop (about 1/4 cup capacity, see note 4). Scoop about a tablespoon of pale yellow cookie dough into the scoop. Next, scoop out some of the swirled black sesame dough (about 2 tablespoons). Continue alternating between the pale yellow dough and the swirled black sesame dough until you have filled up the scoop with cookie dough. (See note 5)
Release the cookie dough from the scoop. I don't usually weigh the cookie dough, but for reference, each cookie should be about 80 to 85 grams. If there's too much pale yellow dough at the top, pinch some black sesame dough and spread it over the pale yellow portion. This will make the top look more marbled.
Add 1/4 teaspoon of white sesame seeds into a small bowl. Roll the rounded top of the cookie dough in the bowl with the sesame seeds until the surface is covered in seeds. Transfer the cookie dough to a lined sheet pan. Continue shaping 3 more portions of cookie dough and topping each portion with 1/4 teaspoon of sesame seeds.
These cookies spread quite a bit, so bake 4 cookies at a time on a half-sheet baking pan. You'll also bake these cookies one sheet at a time, so chill the remaining cookie dough as the first batch of cookies are in the oven.
After shaping several cookies, I like to use a silicone spatula to scrape off the dough from the inside of the scoop.
Bake the cookies for 8 minutes. Wearing oven mitts or using pot holders, grab onto the baking sheet and lift it several inches above the oven rack. Bang the cookie sheet onto the rack to bang the cookies. The cookies should deflate slightly and create a ripple around the edges. Rotate the baking sheet to ensure even baking. Bake the cookies for another 2 minutes. The cookies should have puffed up again. Wear oven mitts or use pot holders to bang the cookies again. Continue baking and banging the cookies at 2-minute intervals 2 more times, until you have baked the cookies for a total of 14 minutes. The edges of the cookies should be a golden brown color. If the edges are not brown enough, bake for another minute.
Take the cookies out of the oven and let them cool for 15 minutes. The centers of the cookies are very soft at this point. The cookies need to cool on the sheet so the centers can set. If you baked the cookies on foil, slide a large flat spatula under the cookies to lift them off the sheet and transfer to a cooling rack. If you baked the cookies on parchment paper, they should come right off the parchment.
As the first batch of cookies cools, prepare another batch of cookies and bake them using the cooking times specified above. Continue until you've baked all the remaining dough.
These cookies taste best once they have cooled completely. Store the cookies in a container for up to 3 days.