Black Sesame Sugar Cookies

For the Black Sesame Sugar:
(makes slightly more than 1 cup)
1/3 cup black sesame seeds
1/3 cup granulated sugar
1/3 cup dark brown sugar

For the Black Sesame Sugar Cookies:
(makes around 24 cookies)
3 1/3 cups all-purpose flour
1 1/2 teaspoons baking powder
1/2 teaspoon kosher salt
1 cup (2 sticks) unsalted butter, at room temperature
1 cup black sesame sugar
1 large egg
1 teaspoon pure vanilla extract

For the Black Sesame Sugar:
Spread sesame seeds evenly in a non-stick pan over medium heat. Stir and toss the seeds every 3 to 4 minutes to ensure that they're being evenly heated, roasting for a total of 12-15 minutes. To check that the seeds are ready, rub a seed between your fingers. The seed should shatter and crush easily into smaller grains, emitting a nutty and fragrant smell. When the seeds pass this test, immediately transfer to a cooler plate on a wire rack to prevent any burning.
Once the seeds cool off completely, transfer to a small bowl and whisk in sugars. Divide into two batches and pulse half the mixture in a food processor until finely ground for about 20 seconds - until the mixture resembles fine cornmeal. Repeat for second half of mixture. (Splitting the ingredients into two batches avoids over processing of the sesame seeds.) Transfer to an airtight container and refrigerate until ready to use.

For the Black Sesame Sugar Cookies:
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
Using an electric mixture with the paddle attachment, combine unsalted butter and 1 cup black sesame sugar. Cream on medium-high speed until light and fluffy, at least 5 minutes. Lower the mixer speed to its lowest setting and add egg and vanilla extract, before turning the mixer speed back to medium-high and beating for an additional minute.
Add dry ingredients and continue mixing on the lowest speed just until the dry ingredients are incorporated, using a rubber spatula to scrape down the sides of the bowl as necessary.
Use your hands to form the dough into a disc and wrap in plastic wrap. Chill in the refrigerator for 1 hour.
Prepare two baking sheets by lining each with parchment paper. Center a rack in the oven and preheat to 350 (F). Roll out the chilled dough on a lightly floured surface to 1/4-inch thick. Cut the dough using your favorite cookie cutter and transfer the cutouts to the two prepared baking sheets.
Transfer one baking sheet to the refrigerator to chill one set of cookies while the other is baking. Transfer the remaining baking sheet to the center rack of the oven and bake for 10 minutes, until the cookies are slightly golden on the edges. Transfer to a wire rack to cool completely. Repeat with the remaining tray of cookies.

*Alternatively, the dough may be formed into 2 1-1/2 inch square logs and refrigerated. Before baking, cut logs into 1/4- inch thick cookies.
**Once completely cooled, serve with a small spoonful of Sweet Lemon Butter on top of each cookie, or sandwiched between two cookies.