Cream butter and sugar using an electric beater for about 1 minute or until smooth and creamy. Add egg white or yolk and vanilla, cream for another minute.Pro tip: Use egg white if you like a light and crisp cookie. And egg yolk if you want a tender and softer cookie.
Add minced walnuts, flour and salt. Continue mixing until it forms a dough.Tip: To mince walnuts, add walnuts into a food processor and process until they are finely minced. Don't make them into a fine powder!
Shape dough into a flat disc and roll between two sheets of parchment paper, until ⅛-inch thick. Transfer dough, along with parchment papers, onto a baking sheet and place in the refrigerator for at least 4 hours (up to one day), until firm.Trouble shooting - If your cookie dough appears dry and crumbly when rolling, incorporate 1 or 2 teaspoons of milk. Conversely, if the dough is sticky, add a bit more flour.
Bake
Preheat oven to 325°F and line two baking sheets with parchment paper.
Remove dough from refrigerator, cut circles using a 3-inch fluted round cookie cutter.
Place cut circles in prepared baking sheets, about an inch apart.
Bake cookies, one sheet at a time, until deep golden in color (22 to 27 minutes). Place baking sheet on a wire rack to cool completely.Pro tip: Refrigerate the second baking sheet of cookie dough while you bake the first batch.
Video
Notes
Chop walnuts very fine - Ensure that no walnut pieces are larger than ¼-inch , avoiding coarse pieces and preventing making them into a fine powder.Chill dough – I recommend chilling both the rolled dough and shaped Halloween trees for several hours, which gives ample time for the dough to firm up before baking.