• Preheat the oven to 375°F with a rack in the center.
• In the bowl of a stand mixer with the paddle attachment, add the butter, sugar, milk powder, confectioners' sugar, lemon or orange zest and milk powder.
• Beat on medium speed for 2 minutes until the ingredients are well combined.
• Scrape the bowl with a silicone spatula. Add the egg yolk and vanilla extract. Beat on medium until combined.
• Add the flour and mix on low until just combined. Finish forming a dough ball with your hands.
• Roll out the dough on 2 pieces of parchment paper. I like to roll the dough about ¼ inch thick for these cookies but you can roll it thinner for a crispier finished product.
• Cut the cookie shapes and use an offset spatula to transfer them into a baking sheet. Use a light color baking sheet (silver preferably).
• You can re roll any cookie scraps into a ball and repeat the process.
• Bake the cookies for about 9 minutes for a soft cookie and up to 12 minutes for a more snappy texture.

Royal icing

• In the bowl of a stand mixer fitted with the whisk attachment, combine all the ingredients and beat on high for 5 minutes.
• Divide the icing into small bowls and add gel food coloring of choice to each bowl.
• Add a teaspoon of water to the colored icing as needed to thin it out to the right consistency. If you add too much water, add back a tablespoon of confectioners' sugar.
• I used a small butter knife to add the icing to my cookies and spread it evenly around. You can use a pipping bag for a more detailed application.
• The consistency of the icing should be not too thick or too thin in order to have it stick to the cookies. Use a toothpick to spread the icing around the edges of the cookies.
• Decorate with Christmas sprinkles and allow the icing to set on a baking rack before storing the cookies.
• Cookies can be stored in an airtight container for up to a week.