Yields 12 medium cookies
2 large egg whites
1/3 cup granulated sugar
1/4 teaspoon coarse salt
1/2 teaspoon vanilla extract
1/3 cup plus 1 tablespoon all-purpose flour
4 tablespoons (2 oz.) unsalted butter melted
1/2 cup toasted white sesame seeds
1/2 cup toasted black sesame seeds
Preheat the oven to 350°F (180°C) and line two large rimmed baking sheets with silicone baking mats.
In a medium bowl, whisk the egg whites vigorously until light, foamy, and pale, 1 1/2 to 2 minutes. Add the sugar, salt, and vanilla extract and whisk until the sugar has fully dissolved.
Add the flour and melted butter, whisking until combined. Stir in the sesame seeds and mix until the seeds are evenly dispersed in the batter. (The batter should be thin, like pancake batter.)
Using a 1 1/2-tablespoon cookie scoop or spoon, drop the batter onto the prepared baking sheets, spacing 2 inches (5 cm) apart. Fit six rounds per sheet; the cookies spread as they bake. Smack the baking sheets a few times on the counter to help flatten the cookies.
Bake one sheet at a time, until the edges of the cookies are golden brown, 14 to 16 minutes. Transfer the sheet to wire racks, and allow the cookies to cool on the sheet for 5 minutes.
Using an offset spatula, transfer the cookies to the rack to cool completely (they will continue to crisp as they cool). Serve warm or at room temperature. Cookies can be stored in an airtight container (a resealable bag works great) at room temperature for up to 4 days, but the longer they sit, the more they lose their crisp texture.
Recipe comes from Mooncakes and Milk Bread: Sweet and Savory Recipes Inspired by Chinese Bakeries by Kristina Cho