Chinese Walnut Cookies (核桃酥)

Prepare the dough

1. Toast the walnuts on the stovetop or in the oven, until very fragrant. If you have a food processor, pulse the walnuts until mostly turned to fine pieces but with corn sized pieces here and there. Without a food processor, place the walnuts into a large ziploc bag and hit it with a rolling pin, until finely crushed with larger pieces here and there.
2. In a medium bowl, whisk together flour, baking soda, baking powder, cornstarch, and salt. Add walnuts and whisk to combine.
3. Add butter and sugar into the bowl of a stand mixer. Attach the whisk to the stand mixer. Turn to medium speed (speed 4 to 6) for about 5 minutes, scraping down sides of bowl halfway through, until the butter lightens in color and the sugar is mostly dissolved. If you don’t have a mixer, you can hand whisk to cream the butter as well.
4. Add the egg into the mixing bowl. Mix until incorporated. Scrape down the sides of the bowl.
5. Add the dry ingredients from step 2. Mix at low-medium speed until the dough just comes together and no dry spots remain, no more than 30 seconds.
6. Transfer the dough out onto the counter or a clean working surface. Divide into 4 equal pieces. Pull a sheet of plastic wrap from the dispenser, leaving the end attached. Put one piece of dough onto the plastic wrap and shape into a log using your hands, rolling back and forth until the log is an even 1” (2.5 cm) in diameter. Rip plastic wrap and roll dough log with plastic to seal. Place the dough into a tray. Repeat with 3 remaining pieces of dough. Refrigerate the dough pieces until solid, at least 2 hours or overnight.

Garnish and bake the cookies

1. Preheat the oven to 350°F (177°C). Line a baking sheet with parchment paper.
2. (Optional) To make the cookies with the raw sugar edges - Brush egg wash #1 onto each dough log. Sprinkle the raw sugar onto a large cutting board. Gently roll the brushed dough log back and forth over the sugar until fully covered.
3. Slice off both ends, then slice each dough into 1/4” (6mm) rounds and place onto the lined baking sheet, with the space of one cookie dough in between. You will need to bake in batches.
4. To garnish the top, brush cookies lightly with egg wash. For a lighter colored surface, use egg wash #1. For a bright yellow color, use egg wash #2. Top with a sprinkle of raw sugar, or a big piece of walnut, or a few small pieces of chopped walnut. (*Footnote 2)
5. Bake at 350°F (177°C) for 120 to 15 minutes, rotating pan halfway through, until golden brown on edges and fragrant. Let the walnut cookies cool off a few minutes, then carefully move to a rack or plate to cool completely before serving.
6. Once cooled completely, store the cookies in a ziplock bag at room temperature for a week, or in the freezer for up to 3 months.