Dig out your tree-shaped cookie cutter and whip up a batch of these Christmas Tree Cookies! The ornaments are easy to make with crushed candy and they're baked right into the cookie dough. It's like adding decoration and flavour at the same time!
In a mixing bowl, beat together the butter and sugar until well combined. Add the egg and milk. Beat to combine.
Next, add the flour, baking powder, and salt. Beat into the butter and sugar mixture. The dough will be dry and crumbly at first, but keep beating until a dry dough is formed. In some cases, you might need to add one more tablespoon of milk. Knead dough to form a ball.
Cover with plastic wrap and refrigerate for 2 hours.
In the meantime, transfer the hard candy to a food processor and pulse until the candy is completely crushed. If you are using different colours, process the candy in batches and keep the colours separate. Set those aside until you are ready to bake.
Preheat your oven to 350 degrees F. Prepare a baking sheet by lining it with parchment paper or a silicone baking mat. Set aside.
Cut the dough into 4 portions. Working with one portion at a time, roll dough to 1/4 inch thick between two sheets of parchment paper.
Use your cookie cutter to cut the shape of the cookie. Use a metal spatula to transfer the cookie to the prepared baking sheet. Save the leftover dough. Re-roll to make more cookies.
Using a straw, push straight down to cut random holes into the cookie where you would like the ornaments placed. (Not too close together or the colours will blend into each other.)
Fill the holes with the crushed candy, using the colour of your choice. The candy should be level with the top of the cookie. A little more or less will not make a difference. If you get any candy on the cookie, use a small, clean paintbrush to brush the candy into the center hole.
Bake for 8 minutes.
Remove the cookies from the oven and allow them to cool for 5 minutes on a baking sheet. Carefully transfer to a wire cooling rack to finish cooling.
Once the cookies are fully cooled, whisk the confectioner's sugar with milk until smooth. Drizzle it over the cookies and immediately sprinkle with coarse sanding sugar. Allow the icing to dry and set fully before packaging and storing the cookies.