• Preheat oven to 350 degrees. Position the rack to the middle of the oven. 
• In a large mixing bowl, whisk together flour, baking powder and salt. Set aside.
• Using a stand mixer with the paddle attachment or a hand mixer, beat the butter and vegetable shortening until combined. Add sugar and beat until light and fluffy. Beat in eggs, one at a time, and vanilla extract until incorporated. 
• Turn the mixer on low and add the flour mixture. Beat until fully incorporated. 
• Gather dough into a disk, wrap in plastic or wax paper and refrigerate for 30-60 minutes. 
• Take the cookie dough out of the refrigerator. Cut the disk in half and let sit at room temperature for a few minutes. This will make it easier to roll out the dough. Place the other half back in the refrigerator.
• Generously flour the board. Roll out disk to about 1/8-inch thick. Use a variety of star cookie cutters to cut out shapes. Arrange cut outs on a baking sheet 2 inches apart. For each tree cut out three large, three medium, three small and two mini-stars.
• Bake, one sheet at a time, for approximately 8-10 minutes, or until the cookies are just starting to turn golden brown on the bottom. Place like sized cut outs on the same sheet for even baking and cooking times. Remove the baking sheet from the oven. Let the cookies cool on the sheet for about 2 minutes, then transfer to a wire rack and cool completely.
• Gather any leftover scraps. Repeat the rolling, cutting and baking process. Once all the scraps are used repeat with the remaining dough.

Icing

• In a small mixing bowl, beat the butter until creamy. 
• Add powdered sugar, vanilla and milk (a little at a time) and beat until desired consistency is reached.
• Add green gel food coloring and mix tougher until desired color is reached.
• Generously frost cookies with icing. Let dry for several hours or overnight to set.
• Add decorating pearls to the top cookie if desired.

Assembling the tree

• Once the icing has dried, place a large star cookie down on a board. Place a small dot of frosting in the middle of the star. You can also use a pipping bag if that is easier for you. 
• Place the second large star on top, slightly off set. Continue this pattern until all your cookies are used. For a tall and symmetrical tree use three large stars, three medium stars, three small stars and two mini stars. Almost a dozen cookies in one tree!