Easy Christmas Tree Cookies

Sift together the flour, baking powder, salt, and set aside. In a bowl of a stand mixer, fitted with a paddle attachment, cream the butter and sugar until light, about 2-3 minutes. Add vanilla and the egg, mix until combined. Add the dry ingredients in 3 steps and beat just until combined; flatten into a disc, wrap into kitchen plastic and refrigerate for 30 minutes or freeze for 15 minutes. Once the dough has chilled, allow it to sit at room temperature for 5-10 minutes. Preheat the oven to 320 F. Separate the dough into 2 parts; roll in between 2 parchment papers or silicone baking mats to 1/4" - 3/8" thick. For clean cutting and shaping of the cookies, freeze the rolled dough sheets for 15 minutes. Cut the dough with your favorite cookie cutters. Bake on middle rack for 10-15 minutes. Allow the cookies to fully chill after baking before removing them from the parchment or baking mats. Divide the buttercream into separate bowls and color it into as many shades of green as you'd like, from lightest to darkest. Using a tipless piping bag or fitted with Wilton's piping tip 10, pipe the first bottom row of darker shade of buttercream dollops and swipe up with small offset spatula or spoon. Repeat with the remaining buttercream and rows; decorate with sparkling sugar and star/snowflake sprinkles. Enjoy!