People serve many kinds of cookies and candies to guests on Chinese New Year. Walnut cookies are often included.
Preheat the oven to 350°F/180°C/Gas Mark 4.
Beat the butter and sugars together until smooth. Add 2 tablespoons egg and mix until fully blended.
Sift the flour, baking soda (bicarbonate of soda), baking powder, and salt into a large bowl. Sift again. Add to the wet mixture, in batches, and mix into a dough. Stir in the broken walnuts. Transfer the dough to a baking sheet, shape into a disk, and let rest for 30 minutes.
Divide the dough into 32 portions. Roll each portion into a ball in your palms and flatten slightly into a small round cookie. Top each circle, if desired, with a piece of broken walnut and transfer to a baking sheet.
Mix the remaining beaten egg with 1 tablespoon water to make an egg wash. Brush the tops of the cookies. Bake for 18 minutes. Reduce the oven temperature to 325°F/160°C/Gas Mark 3 and bake for another 13 minutes until baked through.
Remove from the oven and set aside to cool. Serve immediately or store in an airtight container for up to 3 days.
Adapted from China: The Cookbook by Kei Lum and Diora Fong Chan (Phaidon, 2016)